erofs: Convert to use bdev_open_by_path()

Convert erofs to use bdev_open_by_path() and pass the handle around.

CC: Gao Xiang <xiang@kernel.org>
CC: Chao Yu <chao@kernel.org>
CC: linux-erofs@lists.ozlabs.org
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230927093442.25915-21-jack@suse.cz
Signed-off-by: Christian Brauner <brauner@kernel.org>