bdev: use bdev_io_min() for statx DIO min IO

We currently rely on the block device logical block size for the
offset alignment. While this *works* it doesn't work with performance
in mind. That's exactly what the minimum_io_size attribute is for.

This would for example enhance performance for DIO on 4k IU drives which
have for example an LBA format of 512 bytes for both HDDs and NVMe.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>