drm/i915: Organize vlv/chv watermarks by plane_id

Store the vlv/chv watermark values in straight up arrays indexed by
enum plane_id. Avoids a lot of useless checks for the plane type when
we don't have to think which structure member we need to access.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-7-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1660,24 +1660,22 @@ struct ilk_wm_values {
 };
 
 struct vlv_pipe_wm {
-	uint16_t primary;
-	uint16_t sprite[2];
-	uint8_t cursor;
+	uint16_t plane[I915_MAX_PLANES];
 };
 
 struct vlv_sr_wm {
 	uint16_t plane;
-	uint8_t cursor;
+	uint16_t cursor;
+};
+
+struct vlv_wm_ddl_values {
+	uint8_t plane[I915_MAX_PLANES];
 };
 
 struct vlv_wm_values {
 	struct vlv_pipe_wm pipe[3];
 	struct vlv_sr_wm sr;
-	struct {
-		uint8_t cursor;
-		uint8_t sprite[2];
-		uint8_t primary;
-	} ddl[3];
+	struct vlv_wm_ddl_values ddl[3];
 	uint8_t level;
 	bool cxsr;
 };