drm/vmwgfx: Unpause overlay on update.

The unpause codepath uses vmw_overlay_update() so we must
unset the paused status.

Signed-off-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>