blkcg: fix double free of new_blkg in blkcg_init_queue

commit 9b54d816e00425c3a517514e0d677bb3cec49258 upstream.

If blkg_create fails, new_blkg passed as an argument will
be freed by blkg_create, so there is no need to free it again.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>