[host1x] Simplify the FFmpeg code a bit more (#243)

This simplifies the FFmpeg code a bit more and removes unused variables left in the code.

Co-authored-by: MaranBr <maranbr@outlook.com>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/243

src/video_core/host1x/ffmpeg/ffmpeg.h

@@ -191,7 +191,6 @@ public:
 private:
     const Decoder& m_decoder;
     AVCodecContext* m_codec_context{};
-    s32 m_got_frame{};
     std::shared_ptr<Frame> m_temp_frame{};
     bool m_decode_order{};
 };