scsi: cxgbi: remove redundant __kfree_skb call on skb and free cst->atid

The error return path via label rel_resource checks for a non-null skb
before free'ing it.  However, skb is always null at this exit path, so the
null check and the free are redundant and can be removed.  Removing this
allows the original goto's to rel_resource to be cleaned up; the first can
be replaced by a return of -EINVAL, the second can be replaced by a more
appropriate -ENOMEM return and fix a memory leak by freeing csk->atid.

Addresses-Coverity: ("Logically Dead Code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>