Use audio_mode_t consistently

It was int or uint32_t.
Also make getMode() const.

Change-Id: Ibe45aadbf413b9158e4dd17f2b3bcc6355288d37
diff --git a/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 9d4137e..31a3b53 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -156,7 +156,7 @@
     return NO_ERROR;
 }
 
-status_t AudioSystem::setMode(int mode)
+status_t AudioSystem::setMode(audio_mode_t mode)
 {
     if (uint32_t(mode) >= AUDIO_MODE_CNT) return BAD_VALUE;
     const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
@@ -536,7 +536,7 @@
     return aps->getDeviceConnectionState(device, device_address);
 }
 
-status_t AudioSystem::setPhoneState(int state)
+status_t AudioSystem::setPhoneState(audio_mode_t state)
 {
     const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();
     if (aps == 0) return PERMISSION_DENIED;