Current GuC firmwares identify response message in a different way.

v2: update comments for other H2G bits (Daniele)
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Kelvin Gardiner <kelvin.gardiner@intel.com>
Cc: John Spotswood <john.a.spotswood@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190527183613.17076-14-michal.wajdeczko@intel.com