virtio-blk: only clear VIRTIO_F_ANY_LAYOUT for legacy device

virtio-blk: only clear VIRTIO_F_ANY_LAYOUT for legacy device

Chapter 6.3 of spec said

"
Transitional devices MUST offer, and if offered by the device
transitional drivers MUST accept the following:

VIRTIO_F_ANY_LAYOUT (27)
"

So this patch only clear VIRTIO_F_LAYOUT for legacy device.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>