ocfs2: convert inode refcount test to a helper

Replace the open-coded inode refcount flag test with a helper function
to reduce the potential for bugs.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/ocfs2/alloc.c

@@ -5713,8 +5713,7 @@ int ocfs2_remove_btree_range(struct inode *inode,
 	struct ocfs2_refcount_tree *ref_tree = NULL;
 
 	if ((flags & OCFS2_EXT_REFCOUNTED) && len) {
-		BUG_ON(!(OCFS2_I(inode)->ip_dyn_features &
-			 OCFS2_HAS_REFCOUNT_FL));
+		BUG_ON(!ocfs2_is_refcount_inode(inode));
 
 		if (!refcount_tree_locked) {
 			ret = ocfs2_lock_refcount_tree(osb, refcount_loc, 1,