vdpa: map shadow vrings with MAP_SHARED

vdpa: map shadow vrings with MAP_SHARED

The vdpa devices that use va addresses neeeds these maps shared.
Otherwise, vhost_vdpa checks will refuse to accept the maps.

The mmap call will always return a page aligned address, so removing the
qemu_memalign call.  Keeping the ROUND_UP for the size as we still need
to DMA-map them in full.

Not applying fixes tag as it never worked with va devices.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230602143854.1879091-4-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>