scsi: lpfc: Fix alloc context on oas lun creations

Softlockups are seen in low memory situations. They are due to doing
oas_lun allocation with GFP_KERNEL in atomic contexts.

Change the calls to oas_lun to indicate atomic context so that GFP_ATOMIC
is used.

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>