gallium/nir/tgsi: add support for compact variables

vulkan tessellation uses compact variables for tess factors,
and trips over in the nir->tgsi info gathering, add support
to the info extraction for compact inputs and outputs.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6339>
1 file changed