drdb: Convert to use bdev_open_by_path()

Convert drdb to use bdev_open_by_path().

CC: drbd-dev@lists.linbit.com
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230927093442.25915-4-jack@suse.cz


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