spirv: Add support for subgroup arithmetic

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

src/compiler/shader_info.h

@@ -45,6 +45,7 @@ struct spirv_supported_capabilities {
    bool variable_pointers;
    bool storage_16bit;
    bool shader_viewport_index_layer;
+   bool subgroup_arithmetic;
    bool subgroup_ballot;
    bool subgroup_basic;
    bool subgroup_quad;