virtio: blk: support block sizes exceeding 512 bytes

virtio: blk: support block sizes exceeding 512 bytes

QEMU allows to specify the logical block size via parameter
logical_block_size of a virtio-blk-device.

The communication channel via virtqueues remains based on 512 byte blocks
even if the logical_block_size is larger.

Consider the logical block size in the block device driver.

Reported-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>