spirv: Don't leak GS initialization to other stages
The stage specific fields of shader_info are in an union. We've
likely been lucky that this value was either overwritten or ignored by
other stages. The recent change in shader_info layout in commit
84a1a2578da ("compiler: pack shader_info from 160 bytes to 96 bytes")
made this issue visible.
Fixes:
cf2257069cb ("nir/spirv: Set a default number of invocations for geometry shaders")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>