CDROM: Add option to speed up double speed reads

src/core/settings.h

@@ -123,6 +123,7 @@ struct Settings
   bool cdrom_region_check = true;
   bool cdrom_load_image_to_ram = false;
   bool cdrom_mute_cd_audio = false;
+  u32 cdrom_read_speedup = 1;
 
   AudioBackend audio_backend = AudioBackend::Cubeb;
   s32 audio_output_volume = 100;