aacraid: Removed unnecessary checks for NULL

Current driver checks for NULL return from aac_fib_alloc_tag, but it not
possible for it to return NULL.

Fixed by: Remove all the checks for NULL returns from aac_fib_alloc_tag

Suggested-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>