pan/mdg: Model zero/sign extension for 8/16-bit loads

The destinations are packed as if 32-bit even for 8/16-bit loads, so the mask
needs to be constructed accordingly.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14888>
1 file changed