virtio-blk: Add validation for block size in config space

An untrusted device might presents an invalid block size
in configuration space. This tries to add validation for it
in the validate callback and clear the VIRTIO_BLK_F_BLK_SIZE
feature bit if the value is out of the supported range.

And we also double check the value in virtblk_probe() in
case that it's changed after the validation.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Link: https://lore.kernel.org/r/20210809101609.148-1-xieyongji@bytedance.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>