f2fs: introduce f2fs_has_xattr_block for better readability

This patch introduces a help function f2fs_has_xattr_block for better
readability.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 4dea719..ee6d286 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -242,7 +242,7 @@
 {
 	unsigned int ofs = ofs_of_node(node_page);
 
-	if (ofs == XATTR_NODE_OFFSET)
+	if (f2fs_has_xattr_block(ofs))
 		return false;
 
 	if (ofs == 3 || ofs == 4 + NIDS_PER_BLOCK ||