hal: add DSDA support on APQ targets

-This change adds DSDA support for APQ based targets
 where external modem is used for voice calls.
-Add new CSD API to support local call hold.

Change-Id: I7743a1df43dc1abac4e325ff104ec1bb64c9e12b
diff --git a/hal/msm8960/platform.c b/hal/msm8960/platform.c
index 13f5473..fd62256 100644
--- a/hal/msm8960/platform.c
+++ b/hal/msm8960/platform.c
@@ -895,6 +895,14 @@
     return -ENOSYS;
 }
 
+int platform_update_lch(void *platform __unused,
+                        struct voice_session *session __unused,
+                        enum voice_lch_mode lch_mode __unused)
+{
+    LOGE("%s: Not implemented", __func__);
+    return -ENOSYS;
+}
+
 /* Delay in Us */
 int64_t platform_render_latency(audio_usecase_t usecase)
 {