block: fix module reference leakage from bdev_open_by_dev error path

At the time bdev_may_open() is called, module reference is grabbed
already, hence module reference should be released if bdev_may_open()
failed.

This problem is found by code review.

Fixes: ed5cc702 ("block: Add config option to not allow writing to mounted devices")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240406090930.2252838-22-yukuai1@huaweicloud.com


Signed-off-by: Christian Brauner <brauner@kernel.org>