scsi: qla2xxx: Fix an endian bug in fcpcmd_is_corrupted()

We should first do the le16_to_cpu endian conversion and then apply the
FCP_CMD_LENGTH_MASK mask.

Fixes: 5f35509d ("qla2xxx: Terminate exchange if corrupted")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Quinn Tran <Quinn.Tran@cavium.com>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>