[host1x] fix ffmpeg not having va-api on freebsd, inline nvenc (#3878)

- fix va-api not being used on freebsd

small thingies dont affect a lot:
- removes some pointer indirection (why save pointer to GMMU if its accesible via host1x)
- use std::variant<> for decoder
- miscelly vp9/v8/h264 opts
Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3878
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/video_core/gpu.cpp

@@ -89,7 +89,7 @@ struct GPU::Impl {
         renderer = std::move(renderer_);
         rasterizer = renderer->ReadRasterizer();
         host1x.MemoryManager().BindInterface(rasterizer);
-        host1x.GMMU().BindRasterizer(rasterizer);
+        host1x.gmmu_manager.BindRasterizer(rasterizer);
     }
 
     /// Flush all current written commands into the host GPU for execution.