f2fs: fix to destroy sbi->post_read_wq in error path of f2fs_fill_super()

In error path of f2fs_fill_super(), this patch fixes to call
f2fs_destroy_post_read_wq() once if we fail in f2fs_start_ckpt_thread().

Fixes: 261eeb9c ("f2fs: introduce checkpoint_merge mount option")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -4531,9 +4531,9 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	f2fs_destroy_node_manager(sbi);
 free_sm:
 	f2fs_destroy_segment_manager(sbi);
-	f2fs_destroy_post_read_wq(sbi);
 stop_ckpt_thread:
 	f2fs_stop_ckpt_thread(sbi);
+	f2fs_destroy_post_read_wq(sbi);
 free_devices:
 	destroy_device_list(sbi);
 	kvfree(sbi->ckpt);