libalsa-intf: Add mono headset support

- Some customers use mono device such as mono headset or mono
  speaker in their platform
- Add the mono headset acdb define

CRs-Fixed: 443365
Change-Id: I1ceba40e6329749bf73c366d8c4cbb76b7ca2830
diff --git a/libalsa-intf/msm8960_use_cases.h b/libalsa-intf/msm8960_use_cases.h
index bf4e408..03fffba 100644
--- a/libalsa-intf/msm8960_use_cases.h
+++ b/libalsa-intf/msm8960_use_cases.h
@@ -50,6 +50,7 @@
 #define DEVICE_SPEAKER_STEREO_RX_ACDB_ID                15// SPKR_PHONE_SPKR_STEREO
 #define DEVICE_SPEAKER_TX_ACDB_ID                       11// SPKR_PHONE_MIC
 #define DEVICE_HEADSET_RX_ACDB_ID                       10// HEADSET_SPKR_STEREO
+#define DEVICE_HEADSET_MONO_RX_ACDB_ID                  9 // HEADSET_SPKR_MONO
 #define DEVICE_HEADSET_TX_ACDB_ID                       8 // HEADSET_MIC
 #define DEVICE_DUALMIC_HANDSET_TX_BROADSIDE_ACDB_ID     5 // HANDSET_MIC_BROADSIDE
 #define DEVICE_DUALMIC_HANDSET_TX_ENDFIRE_ACDB_ID       6 // HANDSET_MIC_ENDFIRE