block/io: bdrv_refresh_limits(): use ERRP_GUARD

This simplifies following commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201203222713.13507-3-vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/io.c

@@ -135,10 +135,10 @@ static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
 
 void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
 {
+    ERRP_GUARD();
     BlockDriver *drv = bs->drv;
     BdrvChild *c;
     bool have_limits;
-    Error *local_err = NULL;
 
     memset(&bs->bl, 0, sizeof(bs->bl));
 
@@ -156,9 +156,8 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
     QLIST_FOREACH(c, &bs->children, next) {
         if (c->role & (BDRV_CHILD_DATA | BDRV_CHILD_FILTERED | BDRV_CHILD_COW))
         {
-            bdrv_refresh_limits(c->bs, &local_err);
-            if (local_err) {
-                error_propagate(errp, local_err);
+            bdrv_refresh_limits(c->bs, errp);
+            if (*errp) {
                 return;
             }
             bdrv_merge_limits(&bs->bl, &c->bs->bl);