NFC: pn533: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

drivers/nfc/pn533/pn533.c: In function ‘pn533_transceive’:
drivers/nfc/pn533/pn533.c:2142:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (dev->tgt_active_prot == NFC_PROTO_FELICA) {
      ^
drivers/nfc/pn533/pn533.c:2150:2: note: here
  default:
  ^~~~~~~
drivers/nfc/pn533/pn533.c: In function ‘pn533_wq_mi_recv’:
drivers/nfc/pn533/pn533.c:2267:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (dev->tgt_active_prot == NFC_PROTO_FELICA) {
      ^
drivers/nfc/pn533/pn533.c:2276:2: note: here
  default:
  ^~~~~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Addresses-Coverity-ID: 1230487 ("Missing break in switch")
Addresses-Coverity-ID: 1230488 ("Missing break in switch")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>