scsi: qla2xxx: Modify fall-through annotations

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

Cc: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>