scsi: qla2xxx: Introduce a switch/case statement in qlt_xmit_tm_rsp()

This patch improves code readability but does not change any functionality.

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>