scsi: qla2xxx: Complain if a mailbox command times out

This patch fixes the following Coverity complaint:

Unchecked return value (CHECKED_RETURN)
check_return: Calling wait_for_completion_timeout without checking return
value (as is done elsewhere 14 out of 17 times).

Cc: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>