FS-Cache: Wrap checks on object state

Wrap checks on object state (mostly outside of fs/fscache/object.c) with
inline functions so that the mechanism can be replaced.

Some of the state checks within object.c are left as-is as they will be
replaced.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-By: Milosz Tanski <milosz@adfin.com>
Acked-by: Jeff Layton <jlayton@redhat.com>

fs/fscache/cache.c

@@ -115,7 +115,7 @@ struct fscache_cache *fscache_select_cache_for_object(
 				     struct fscache_object, cookie_link);
 
 		cache = object->cache;
-		if (object->state >= FSCACHE_OBJECT_DYING ||
+		if (fscache_object_is_dying(object) ||
 		    test_bit(FSCACHE_IOERROR, &cache->flags))
 			cache = NULL;