gl_rasterizer_cache: Implement RenderTargetFormat BGRA8_UNORM.

src/video_core/gpu.cpp

@@ -38,6 +38,7 @@ u32 RenderTargetBytesPerPixel(RenderTargetFormat format) {
         return 8;
     case RenderTargetFormat::RGBA8_UNORM:
     case RenderTargetFormat::RGB10_A2_UNORM:
+    case RenderTargetFormat::BGRA8_UNORM:
         return 4;
     default:
         UNIMPLEMENTED_MSG("Unimplemented render target format {}", static_cast<u32>(format));