bcachefs: Fix error path in bch2_mount()

This fixes a bug discovered by generic/388 where sb->s_fs_info was NULL
while the superblock was still active - the error path was entirely
fubar, and was trying to do something unclear and unecessary.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs.c

@@ -1922,22 +1922,16 @@ static struct dentry *bch2_mount(struct file_system_type *fs_type,
 	return dget(sb->s_root);
 
 err_put_super:
-	sb->s_fs_info = NULL;
-	c->vfs_sb = NULL;
 	deactivate_locked_super(sb);
-	bch2_fs_stop(c);
 	return ERR_PTR(bch2_err_class(ret));
 }
 
 static void bch2_kill_sb(struct super_block *sb)
 {
 	struct bch_fs *c = sb->s_fs_info;
 
-	if (c)
-		c->vfs_sb = NULL;
 	generic_shutdown_super(sb);
-	if (c)
-		bch2_fs_free(c);
+	bch2_fs_free(c);
 }
 
 static struct file_system_type bcache_fs_type = {