frontends/va: Initialize drm modifier on import.

On import we don't get a modifier so the modifier in the Gallium
handle should be set to DRM_FORMAT_MOD_INVALID instead of LINEAR.

Otherwise things like screen capture break if the driver actually
starts supporting modifiers.

Acked-by: Leo Liu <leo.liu@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7302>
1 file changed