f2fs: add an option to avoid unnecessary BUG_ONs

If you want to remove unnecessary BUG_ONs, you can just turn off F2FS_CHECK_FS
in your kernel config.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index c9d53fc..594fc1b 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -139,7 +139,7 @@
 	bool room = false;
 	int max_slots = 0;
 
-	BUG_ON(level > MAX_DIR_HASH_DEPTH);
+	f2fs_bug_on(level > MAX_DIR_HASH_DEPTH);
 
 	nbucket = dir_buckets(level);
 	nblock = bucket_blocks(level);