scsi: fnic: Validate io_req before others

We need to check for a valid io_req before we check other data. Also,
remove redundant checks.

Link: https://lore.kernel.org/r/20201121023337.19295-1-kartilak@cisco.com


Reviewed-by: Arulprabhu Ponnusamy <arulponn@cisco.com>
Co-developed-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Karan Tilak Kumar <kartilak@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>