gl_rasterizer: Implement render target format RG8_SNORM.

- Used by Super Mario Odyssey.

src/video_core/gpu.cpp

@@ -67,6 +67,7 @@ u32 RenderTargetBytesPerPixel(RenderTargetFormat format) {
     case RenderTargetFormat::R16_UINT:
     case RenderTargetFormat::R16_SINT:
     case RenderTargetFormat::R16_FLOAT:
+    case RenderTargetFormat::RG8_SNORM:
         return 2;
     case RenderTargetFormat::R8_UNORM:
         return 1;