audio: enable 5.1.2 channel mask configuration

- Support query of DP max channels.
- Enable 5.1.2 channel mask configuration.

Change-Id: I0fa6f50fc21189b539ec963f35bd627d4bd261da
diff --git a/hal/msm8916/platform.c b/hal/msm8916/platform.c
index e5e8c19..1d80893 100644
--- a/hal/msm8916/platform.c
+++ b/hal/msm8916/platform.c
@@ -5759,7 +5759,7 @@
         my_data->current_backend_cfg[backend_idx].channels = channels;
 
         if (backend_idx == HDMI_RX_BACKEND)
-            platform_set_edid_channels_configuration(adev->platform, channels);
+            platform_set_edid_channels_configuration(adev->platform, channels, HDMI_RX_BACKEND);
 
         ALOGD("%s:becf: afe: %s set to %s", __func__,
                my_data->current_backend_cfg[backend_idx].channels_mixer_ctl, channel_cnt_str);
@@ -7091,7 +7091,7 @@
     return false;
 }
 
-int platform_set_edid_channels_configuration(void *platform, int channels) {
+int platform_set_edid_channels_configuration(void *platform, int channels, int backend_idx __unused) {
 
     struct platform_data *my_data = (struct platform_data *)platform;
     struct audio_device *adev = my_data->adev;