Hearing Aid volume curve

Hearing Aid uses volume value from -127 to 0dB. Make sure that volume
curve used is able to adjust volume in whole range.

Test: play music using Hearing Aid, try lowering volume to smallest
non-mute value.
Bug: 69623109
Fixes: 76434849
Change-Id: I8b8d64405016252f08ddda823fab74115352de4e
diff --git a/services/audiopolicy/common/include/Volume.h b/services/audiopolicy/common/include/Volume.h
index 4862684..fc012a2 100644
--- a/services/audiopolicy/common/include/Volume.h
+++ b/services/audiopolicy/common/include/Volume.h
@@ -38,6 +38,7 @@
     DEVICE_CATEGORY_SPEAKER,
     DEVICE_CATEGORY_EARPIECE,
     DEVICE_CATEGORY_EXT_MEDIA,
+    DEVICE_CATEGORY_HEARING_AID,
     DEVICE_CATEGORY_CNT
 };
 
@@ -125,8 +126,9 @@
         case AUDIO_DEVICE_OUT_BLUETOOTH_A2DP:
         case AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES:
         case AUDIO_DEVICE_OUT_USB_HEADSET:
-        case AUDIO_DEVICE_OUT_HEARING_AID:
             return DEVICE_CATEGORY_HEADSET;
+        case AUDIO_DEVICE_OUT_HEARING_AID:
+            return DEVICE_CATEGORY_HEARING_AID;
         case AUDIO_DEVICE_OUT_LINE:
         case AUDIO_DEVICE_OUT_AUX_DIGITAL:
         case AUDIO_DEVICE_OUT_USB_DEVICE: