DS GX: Fix incorrect W values

CHANGES

@@ -9,6 +9,7 @@ Bugfixes:
  - DS Video: Fix display capture blending value 16 (fixes mgba.io/i/757)
  - DS GX: Properly center cross product in polygon normal calculations
  - DS Video: Fix affine parameter advancing (fixes mgba.io/i/802)
+ - DS GX: Fix incorrect W values
 Misc:
  - DS GX: Clean up and unify texture mapping
  - DS Core: Add symbol loading

src/ds/gx.c

@@ -408,7 +408,7 @@ static int32_t _dotViewport(struct DSGXVertex* vertex, int32_t* col) {
 	a = col[12];
 	b = MTX_ONE;
 	sum += a * b;
-	return sum >> 8LL;
+	return sum >> 12LL;
 }
 
 static int16_t _dotTexture(struct DSGX* gx, int16_t* input, int mode, int c) {