misc: sgi-gru: fix return of error

If kzalloc() fails then gms is NULL and we are returning NULL, but the
functions which called this function gru_register_mmu_notifier() are not
expecting NULL as the return. They are expecting either a valid pointer
or the error code in ERR_PTR.
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Acked-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/sgi-gru/grutlbpurge.c

@@ -306,7 +306,8 @@ struct gru_mm_struct *gru_register_mmu_notifier(void)
 		atomic_inc(&gms->ms_refcnt);
 	} else {
 		gms = kzalloc(sizeof(*gms), GFP_KERNEL);
-		if (gms) {
+		if (!gms)
+			return ERR_PTR(-ENOMEM);
 		STAT(gms_alloc);
 		spin_lock_init(&gms->ms_asid_lock);
 		gms->ms_notifier.ops = &gru_mmuops;
@@ -316,7 +317,6 @@ struct gru_mm_struct *gru_register_mmu_notifier(void)
 		if (err)
 			goto error;
 	}
-	}
 	if (gms)
 		gru_dbg(grudev, "gms %p, refcnt %d\n", gms,
 			atomic_read(&gms->ms_refcnt));