panfrost: Size UBO#0 accurately

We explicitly calculated its size as (sysvals + uniforms). We don't need
to check the shader metadata for that.

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/6440>