xfs: sync xfs_btree_split macros with userspace libxfs

Sync this one last bit of discrepancy between kernel and userspace
libxfs.
Signed-off-by: NDarrick J. Wong <djwong@kernel.org>
Reviewed-by: NEric Sandeen <sandeen@redhat.com>

fs/xfs/libxfs/xfs_btree.c

@@ -2785,6 +2785,7 @@ __xfs_btree_split(
 	return error;
 }
 
+#ifdef __KERNEL__
 struct xfs_btree_split_args {
 	struct xfs_btree_cur	*cur;
 	int			level;
@@ -2870,6 +2871,9 @@ xfs_btree_split(
 	destroy_work_on_stack(&args.work);
 	return args.result;
 }
+#else
+#define xfs_btree_split	__xfs_btree_split
+#endif /* __KERNEL__ */
 
 
 /*