VideoCommon: Add an option to disable mipmaps

Needed by M1 fifoci to work around a minor non-determinism bug

Source/Core/VideoCommon/VideoConfig.h

@@ -143,6 +143,9 @@ struct VideoConfig final
   int iSaveTargetId = 0;  // TODO: Should be dropped
   u32 iMissingColorValue = 0;
   bool bFastTextureSampling = false;
+#ifdef __APPLE__
+  bool bNoMipmapping = false;  // Used by macOS fifoci to work around an M1 bug
+#endif
 
   // Stereoscopy
   StereoMode stereo_mode{};