gpu/internal/driver: use strings for generated DXIL assembly

Literal strings are a more compact than literal byte slices. A future
change will switch to go:embed to save even more space.

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

gpu/internal/driver/driver.go

@@ -59,7 +59,7 @@ type ShaderSources struct {
 	GLSL310ES string
 	GLSL130   string
 	GLSL150   string
-	HLSL      []byte
+	HLSL      string
 	Uniforms  UniformsReflection
 	Inputs    []InputLocation
 	Textures  []TextureBinding