media: siano: Fix out-of-bounds warnings in smscore_load_firmware_family2()

Rename struct sms_msg_data4 to sms_msg_data5 and increase the size of
its msg_data array from 4 to 5 elements. Notice that at some point
the 5th element of msg_data is being accessed in function
smscore_load_firmware_family2():

1006                 trigger_msg->msg_data[4] = 4; /* Task ID */

Also, there is no need for the object _trigger_msg_ of type struct
sms_msg_data *, when _msg_ can be used, directly. Notice that msg_data
in struct sms_msg_data is a one-element array, which causes multiple
out-of-bounds warnings when accessing beyond its first element
in function smscore_load_firmware_family2():

 992                 struct sms_msg_data *trigger_msg =
 993                         (struct sms_msg_data *) msg;
 994
 995                 pr_debug("sending MSG_SMS_SWDOWNLOAD_TRIGGER_REQ\n");
 996                 SMS_INIT_MSG(&msg->x_msg_header,
 997                                 MSG_SMS_SWDOWNLOAD_TRIGGER_REQ,
 998                                 sizeof(struct sms_msg_hdr) +
 999                                 sizeof(u32) * 5);
1000
1001                 trigger_msg->msg_data[0] = firmware->start_address;
1002                                         /* Entry point */
1003                 trigger_msg->msg_data[1] = 6; /* Priority */
1004                 trigger_msg->msg_data[2] = 0x200; /* Stack size */
1005                 trigger_msg->msg_data[3] = 0; /* Parameter */
1006                 trigger_msg->msg_data[4] = 4; /* Task ID */

even when enough dynamic memory is allocated for _msg_:

 929         /* PAGE_SIZE buffer shall be enough and dma aligned */
 930         msg = kmalloc(PAGE_SIZE, GFP_KERNEL | coredev->gfp_buf_flags);

but as _msg_ is casted to (struct sms_msg_data *):

 992                 struct sms_msg_data *trigger_msg =
 993                         (struct sms_msg_data *) msg;

the out-of-bounds warnings are actually valid and should be addressed.

Fix this by declaring object _msg_ of type struct sms_msg_data5 *,
which contains a 5-elements array, instead of just 4. And use
_msg_ directly, instead of creating object trigger_msg.

This helps with the ongoing efforts to enable -Warray-bounds by fixing
the following warnings:

  CC [M]  drivers/media/common/siano/smscoreapi.o
drivers/media/common/siano/smscoreapi.c: In function ‘smscore_load_firmware_family2’:
drivers/media/common/siano/smscoreapi.c:1003:24: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
 1003 |   trigger_msg->msg_data[1] = 6; /* Priority */
      |   ~~~~~~~~~~~~~~~~~~~~~^~~
In file included from drivers/media/common/siano/smscoreapi.c:12:
drivers/media/common/siano/smscoreapi.h:619:6: note: while referencing ‘msg_data’
  619 |  u32 msg_data[1];
      |      ^~~~~~~~
drivers/media/common/siano/smscoreapi.c:1004:24: warning: array subscript 2 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
 1004 |   trigger_msg->msg_data[2] = 0x200; /* Stack size */
      |   ~~~~~~~~~~~~~~~~~~~~~^~~
In file included from drivers/media/common/siano/smscoreapi.c:12:
drivers/media/common/siano/smscoreapi.h:619:6: note: while referencing ‘msg_data’
  619 |  u32 msg_data[1];
      |      ^~~~~~~~
drivers/media/common/siano/smscoreapi.c:1005:24: warning: array subscript 3 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
 1005 |   trigger_msg->msg_data[3] = 0; /* Parameter */
      |   ~~~~~~~~~~~~~~~~~~~~~^~~
In file included from drivers/media/common/siano/smscoreapi.c:12:
drivers/media/common/siano/smscoreapi.h:619:6: note: while referencing ‘msg_data’
  619 |  u32 msg_data[1];
      |      ^~~~~~~~
drivers/media/common/siano/smscoreapi.c:1006:24: warning: array subscript 4 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
 1006 |   trigger_msg->msg_data[4] = 4; /* Task ID */
      |   ~~~~~~~~~~~~~~~~~~~~~^~~
In file included from drivers/media/common/siano/smscoreapi.c:12:
drivers/media/common/siano/smscoreapi.h:619:6: note: while referencing ‘msg_data’
  619 |  u32 msg_data[1];
      |      ^~~~~~~~

Fixes: 018b0c6f ("[media] siano: make load firmware logic to work with newer firmwares")
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>