drm/i915/tgl: Add Wa number to WaAllowPMDepthAndInvocationCountAccessFromUMD

Just to make easier to check that the Wa was implemetend when
comparing to the number in BSpec.

BSpec: 52890
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227220101.321671-10-jose.souza@intel.com

drivers/gpu/drm/i915/gt/intel_workarounds.c

@@ -1254,6 +1254,7 @@ static void tgl_whitelist_build(struct intel_engine_cs *engine)
 	case RENDER_CLASS:
 		/*
 		 * WaAllowPMDepthAndInvocationCountAccessFromUMD:tgl
+		 * Wa_1408556865:tgl
 		 *
 		 * This covers 4 registers which are next to one another :
 		 *   - PS_INVOCATION_COUNT