scsi: fnic: Refactor code in fnic probe to initialize SCSI layer

scsi: fnic: Refactor code in fnic probe to initialize SCSI layer

Refactor code from fnic probe into a different function so that
scsi layer initialization code is grouped together.
Also, add log messages for better debugging.

Link: https://lore.kernel.org/r/20220707205155.692688-1-kartilak@cisco.com
Co-developed-by: Gian Carlo Boffa <gcboffa@cisco.com>
Signed-off-by: Gian Carlo Boffa <gcboffa@cisco.com>
Co-developed-by: Arulprabhu Ponnusamy <arulponn@cisco.com>
Signed-off-by: Arulprabhu Ponnusamy <arulponn@cisco.com>
Signed-off-by: Karan Tilak Kumar <kartilak@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>