compiler: Add two new system values for subgroups

This will be required for SPIR-V subgroup support

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

src/compiler/shader_enums.c

@@ -210,6 +210,8 @@ gl_system_value_name(gl_system_value sysval)
      ENUM(SYSTEM_VALUE_SUBGROUP_GT_MASK),
      ENUM(SYSTEM_VALUE_SUBGROUP_LE_MASK),
      ENUM(SYSTEM_VALUE_SUBGROUP_LT_MASK),
+     ENUM(SYSTEM_VALUE_NUM_SUBGROUPS),
+     ENUM(SYSTEM_VALUE_SUBGROUP_ID),
      ENUM(SYSTEM_VALUE_VERTEX_ID),
      ENUM(SYSTEM_VALUE_INSTANCE_ID),
      ENUM(SYSTEM_VALUE_INSTANCE_INDEX),