f2fs: remove false-positive bug_on

For example,

f2fs_create
 - new_node_page is failed
 - handle_failed_inode
  - skip to add it into orphan list, since ni.blk_addr == NULL_ADDR
   : set_inode_flag(inode, FI_FREE_NID)

f2fs_evict_inode
 - EIO due to fault injection
 - f2fs_bug_on() is triggered

So, we don't need to call f2fs_bug_on in this case.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/inode.c

@@ -425,9 +425,10 @@ void f2fs_evict_inode(struct inode *inode)
 	if (is_inode_flag_set(inode, FI_FREE_NID)) {
 		alloc_nid_failed(sbi, inode->i_ino);
 		clear_inode_flag(inode, FI_FREE_NID);
-	}
+	} else {
 		f2fs_bug_on(sbi, err &&
 			!exist_written_data(sbi, inode->i_ino, ORPHAN_INO));
+	}
 out_clear:
 	fscrypt_put_encryption_info(inode, NULL);
 	clear_inode(inode);