s390/zcrypt: adjust switch fall through comments for -Wimplicit-fallthrough

Silence the following warnings when built with -Wimplicit-fallthrough=3
enabled by default since 5.3-rc2:
In file included from ./include/linux/preempt.h:11,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/mmzone.h:8,
                 from ./include/linux/gfp.h:6,
                 from ./include/linux/slab.h:15,
                 from drivers/s390/crypto/ap_queue.c:13:
drivers/s390/crypto/ap_queue.c: In function 'ap_sm_recv':
./include/linux/list.h:577:2: warning: this statement may fall through [-Wimplicit-fallthrough=]
  577 |  for (pos = list_first_entry(head, typeof(*pos), member); \
      |  ^~~
drivers/s390/crypto/ap_queue.c:147:3: note: in expansion of macro 'list_for_each_entry'
  147 |   list_for_each_entry(ap_msg, &aq->pendingq, list) {
      |   ^~~~~~~~~~~~~~~~~~~
drivers/s390/crypto/ap_queue.c:155:2: note: here
  155 |  case AP_RESPONSE_NO_PENDING_REPLY:
      |  ^~~~
drivers/s390/crypto/zcrypt_msgtype6.c: In function 'convert_response_ep11_xcrb':
drivers/s390/crypto/zcrypt_msgtype6.c:871:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
  871 |   if (msg->cprbx.cprb_ver_id == 0x04)
      |      ^
drivers/s390/crypto/zcrypt_msgtype6.c:874:2: note: here
  874 |  default: /* Unknown response type, this should NEVER EVER happen */
      |  ^~~~~~~
drivers/s390/crypto/zcrypt_msgtype6.c: In function 'convert_response_rng':
drivers/s390/crypto/zcrypt_msgtype6.c:901:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
  901 |   if (msg->cprbx.cprb_ver_id == 0x02)
      |      ^
drivers/s390/crypto/zcrypt_msgtype6.c:907:2: note: here
  907 |  default: /* Unknown response type, this should NEVER EVER happen */
      |  ^~~~~~~
drivers/s390/crypto/zcrypt_msgtype6.c: In function 'convert_response_xcrb':
drivers/s390/crypto/zcrypt_msgtype6.c:838:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
  838 |   if (msg->cprbx.cprb_ver_id == 0x02)
      |      ^
drivers/s390/crypto/zcrypt_msgtype6.c:844:2: note: here
  844 |  default: /* Unknown response type, this should NEVER EVER happen */
      |  ^~~~~~~
drivers/s390/crypto/zcrypt_msgtype6.c: In function 'convert_response_ica':
drivers/s390/crypto/zcrypt_msgtype6.c:801:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
  801 |   if (msg->cprbx.cprb_ver_id == 0x02)
      |      ^
drivers/s390/crypto/zcrypt_msgtype6.c:808:2: note: here
  808 |  default: /* Unknown response type, this should NEVER EVER happen */
      |  ^~~~~~~

Acked-by: Patrick Steuer <patrick.steuer@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>