hal: add USB capture backend configuration support

Add USB capture BE configuration support and update the parsing
function to retrieve USB device capability.

Change-Id: I3dc7d289b3fcc96d522a2df3b8168f546737c036
CRs-Fixed: 1050510 1054988 1050666 1058845
diff --git a/hal/msm8916/platform.h b/hal/msm8916/platform.h
index 516a298..1e54ee1 100644
--- a/hal/msm8916/platform.h
+++ b/hal/msm8916/platform.h
@@ -209,7 +209,6 @@
 #define MAX_PORT                        6
 #define ALL_CODEC_BACKEND_PORT          0
 #define HEADPHONE_44_1_BACKEND_PORT     5
-#define MAX_CODEC_TX_BACKENDS           1
 enum {
     DEFAULT_CODEC_BACKEND,
     SLIMBUS_0_RX = DEFAULT_CODEC_BACKEND,
@@ -224,6 +223,12 @@
     USB_AUDIO_RX_BACKEND,
     MAX_CODEC_BACKENDS
 };
+enum {
+    DEFAULT_CODEC_TX_BACKEND,
+    SLIMBUS_0_TX = DEFAULT_CODEC_TX_BACKEND,
+    USB_AUDIO_TX_BACKEND,
+    MAX_CODEC_TX_BACKENDS
+};
 #define AUDIO_PARAMETER_KEY_NATIVE_AUDIO "audio.nat.codec.enabled"
 #define AUDIO_PARAMETER_KEY_NATIVE_AUDIO_MODE "native_audio_mode"