hal: Added support for HFP

 - Added setparameter to be set from hfp app to enable
   and disable hfp session.
 - Implemeted start and stop hfp session which takes
   care of switching device and setting the session

Change-Id: Ie8697328ccbfee09d0d162f6fad01ddb552e4f83
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index 6ff6f40..639032f 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -62,6 +62,9 @@
     /* FM usecase */
     USECASE_AUDIO_PLAYBACK_FM,
 
+    /* HFP Use case*/
+    USECASE_AUDIO_HFP_SCO,
+
     /* Capture usecases */
     USECASE_AUDIO_RECORD,
     USECASE_AUDIO_RECORD_COMPRESS,
@@ -179,7 +182,8 @@
     PCM_PLAYBACK,
     PCM_CAPTURE,
     VOICE_CALL,
-    VOIP_CALL
+    VOIP_CALL,
+    PCM_HFP_CALL
 } usecase_type_t;
 
 union stream_ptr {