panfrost: XMLify attributes

To keep review manageable, this only ports over pandecode and blitting.
The main uses for vertex data and varying linkage will come next, as
they touch considerably more code.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6326>
4 files changed