remoteproc: qcom_q6v5_mss: Validate modem blob firmware size before load

commit 135b9e8d

 upstream.

The following mem abort is observed when one of the modem blob firmware
size exceeds the allocated mpss region. Fix this by restricting the copy
size to segment size using request_firmware_into_buf before load.

Err Logs:
Unable to handle kernel paging request at virtual address
Mem abort info:
...
Call trace:
  __memcpy+0x110/0x180
  rproc_start+0xd0/0x190
  rproc_boot+0x404/0x550
  state_store+0x54/0xf8
  dev_attr_store+0x44/0x60
  sysfs_kf_write+0x58/0x80
  kernfs_fop_write+0x140/0x230
  vfs_write+0xc4/0x208
  ksys_write+0x74/0xf8
...

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Fixes: 051fb70f

 ("remoteproc: qcom: Driver for the self-authenticating Hexagon v5")
Cc: stable@vger.kernel.org
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/20200722201047.12975-3-sibis@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>