spirv: Add subgroup quad support

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/compiler/shader_info.h

@@ -47,6 +47,7 @@ struct spirv_supported_capabilities {
    bool shader_viewport_index_layer;
    bool subgroup_ballot;
    bool subgroup_basic;
+   bool subgroup_quad;
    bool subgroup_shuffle;
    bool subgroup_vote;
 };