drm/i915: Document that PPT==CPT and WPT==LPT

For our purposes PPT is equivalent to CPT, and WPT is equivalent to
LPT. Document that fact.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170620130310.13245-4-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1150,8 +1150,8 @@ struct i915_psr {
 enum intel_pch {
 	PCH_NONE = 0,	/* No PCH present */
 	PCH_IBX,	/* Ibexpeak PCH */
-	PCH_CPT,	/* Cougarpoint PCH */
-	PCH_LPT,	/* Lynxpoint PCH */
+	PCH_CPT,	/* Cougarpoint/Pantherpoint PCH */
+	PCH_LPT,	/* Lynxpoint/Wildcatpoint PCH */
 	PCH_SPT,        /* Sunrisepoint PCH */
 	PCH_KBP,        /* Kabypoint PCH */
 	PCH_CNP,        /* Cannonpoint PCH */