gpu/shaders: update piet-gpu

Changes:
- faster implementation of RGBA output
- fix stroked clips and images

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/shaders/setup.h

@@ -42,7 +42,10 @@ struct Config {
 #define MODE_NONZERO 0
 #define MODE_STROKE 1
 
+// Size of kernel4 clip state, in words.
+#define CLIP_STATE_SIZE 2
+
 // fill_mode_from_flags extracts the fill mode from tag flags.
 uint fill_mode_from_flags(uint flags) {
-	return flags & 0x1;
+    return flags & 0x1;
 }