hal: changes to support 24 bit record

-Changes to support 24 bit record if input format request is
 AUDIO_FORMAT_PCM_8_24_BIT or AUDIO_FORMAT_PCM_24_BIT_PACKED

Change-Id: I68076524ccccbf9f0be3c88bb01180ae7e4fd8b1
diff --git a/hal/msm8974/platform.h b/hal/msm8974/platform.h
index caa40d1..7fe7271 100644
--- a/hal/msm8974/platform.h
+++ b/hal/msm8974/platform.h
@@ -179,7 +179,7 @@
 
 #define DEFAULT_OUTPUT_SAMPLING_RATE    48000
 #define OUTPUT_SAMPLING_RATE_44100      44100
-
+#define MAX_CODEC_TX_BACKENDS           1
 enum {
     DEFAULT_CODEC_BACKEND,
     SLIMBUS_0_RX = DEFAULT_CODEC_BACKEND,