scsi: lpfc: Annotate switch/case fall-through

This patch avoids that the compiler warns about missing fall-through
annotation when building with W=1.

Cc: James Smart <james.smart@broadcom.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>