f2fs: introduce f2fs_kmalloc to wrap kmalloc

This patch adds f2fs_kmalloc.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index dbfc1d1..6bd0595 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -805,7 +805,7 @@
 			int save_len = fstr->len;
 			int ret;
 
-			de_name.name = kmalloc(de_name.len, GFP_NOFS);
+			de_name.name = f2fs_kmalloc(de_name.len, GFP_NOFS);
 			if (!de_name.name)
 				return false;