f2fs: check return value during recovery

This patch resolves Coverity #753102:

>>> No check of the return value of "f2fs_add_link(&dent, inode)".

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 502c63d..6cc046d 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -67,7 +67,7 @@
 		kunmap(page);
 		f2fs_put_page(page, 0);
 	} else {
-		f2fs_add_link(&dent, inode);
+		err = f2fs_add_link(&dent, inode);
 	}
 	iput(dir);
 out: