virtio_blk: add SECURE ERASE command support

Support for the VIRTIO_BLK_F_SECURE_ERASE VirtIO feature.

A device that offers this feature can receive VIRTIO_BLK_T_SECURE_ERASE
commands.

A device which supports this feature has the following fields in the
virtio config:

- max_secure_erase_sectors
- max_secure_erase_seg
- secure_erase_sector_alignment

max_secure_erase_sectors and secure_erase_sector_alignment are expressed
in 512-byte units.

Every secure erase command has the following fields:

- sectors: The starting offset in 512-byte units.
- num_sectors: The number of sectors.

Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
Message-Id: <20220921082729.2516779-1-alvaro.karsz@solid-run.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>