[Xboxkrnl/XConfig] add user audio config

- Allows for user to set their audio type in the config
- Record audio flags and how they function

src/xenia/kernel/xboxkrnl/xboxkrnl_audio.cc

@@ -15,12 +15,14 @@
 #include "xenia/kernel/xboxkrnl/xboxkrnl_private.h"
 #include "xenia/xbox.h"
 
+DECLARE_uint32(audio_flag);
+
 namespace xe {
 namespace kernel {
 namespace xboxkrnl {
 
 dword_result_t XAudioGetSpeakerConfig_entry(lpdword_t config_ptr) {
-  *config_ptr = 0x00010001;
+  *config_ptr = cvars::audio_flag;
   return X_ERROR_SUCCESS;
 }
 DECLARE_XBOXKRNL_EXPORT1(XAudioGetSpeakerConfig, kAudio, kImplemented);