scsi: lpfc: Fix driver crash in target reset handler

It's possible for the scsi error handler to fire and call the target reset
handler simultaneously to the driver logging out and relogging into the
system.  If hit just right, the re-login may not have fully re-established
the remote port and the rdata->pnod structure may be null.

Check for NULL in the reset handler and return failure if NULL.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>