ac/nir: Make shader key a struct.

Some bits can be passed to almost every shader, and I don't like
adding 5 variables.

Reviewed-by: Dave Airlie <airlied@redhat.com>

src/amd/vulkan/radv_pipeline_cache.c

@@ -89,7 +89,7 @@ radv_hash_shader(unsigned char *hash, struct radv_shader_module *module,
 		 const char *entrypoint,
 		 const VkSpecializationInfo *spec_info,
 		 const struct radv_pipeline_layout *layout,
-		 const union ac_shader_variant_key *key,
+		 const struct ac_shader_variant_key *key,
 		 uint32_t is_geom_copy_shader)
 {
 	struct mesa_sha1 ctx;