panfrost: Handle fixed-point packing in GenXML

panfrost: Handle fixed-point packing in GenXML

Minimum/maximum LOD and LOD bias are unsigned and signed fixed point formats
respectively. They are not unsigned integers. Introduce fixed-point types into
our GenXML and use them in the XML, rather than packing in sidebands. This makes
the XML more correct and fixes pretty-printing of texture and sampler
descriptors.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20445>