virtio_blk: mark all zone fields LE

zone is a virtio 1.x feature so all fields are LE,
they are handled as such, but have mistakenly been labeled
__virtioXX in the header.  This results in a bunch of sparse warnings.

Use the __leXX tags to make sparse happy.

Message-Id: <20221222193214.55146-1-mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>