xfs: sync xfs_btree_split macros with userspace libxfs

Sync this one last bit of discrepancy between kernel and userspace
libxfs.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index b4e19aa..f18a875 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -2785,6 +2785,7 @@
 	return error;
 }
 
+#ifdef __KERNEL__
 struct xfs_btree_split_args {
 	struct xfs_btree_cur	*cur;
 	int			level;
@@ -2870,6 +2871,9 @@
 	destroy_work_on_stack(&args.work);
 	return args.result;
 }
+#else
+#define xfs_btree_split	__xfs_btree_split
+#endif /* __KERNEL__ */
 
 
 /*