Use audio_mode_t consistently

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

Change-Id: Ibe45aadbf413b9158e4dd17f2b3bcc6355288d37
diff --git a/services/audioflinger/AudioPolicyService.h b/services/audioflinger/AudioPolicyService.h
index 88cb1e9..4aafdfc 100644
--- a/services/audioflinger/AudioPolicyService.h
+++ b/services/audioflinger/AudioPolicyService.h
@@ -58,7 +58,7 @@
     virtual audio_policy_dev_state_t getDeviceConnectionState(
                                                                 audio_devices_t device,
                                                                 const char *device_address);
-    virtual status_t setPhoneState(int state);
+    virtual status_t setPhoneState(audio_mode_t state);
     virtual status_t setRingerMode(uint32_t mode, uint32_t mask);
     virtual status_t setForceUse(audio_policy_force_use_t usage, audio_policy_forced_cfg_t config);
     virtual audio_policy_forced_cfg_t getForceUse(audio_policy_force_use_t usage);