drm/i915/icl: Add missing power gate enums

On ICL there are 5 fused power gates, so add the two missing ones for
clarity.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180806095843.13294-11-imre.deak@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -8913,6 +8913,8 @@ enum skl_power_gate {
 	SKL_PG0,
 	SKL_PG1,
 	SKL_PG2,
+	ICL_PG3,
+	ICL_PG4,
 };
 
 #define SKL_FUSE_STATUS				_MMIO(0x42000)