audio: hal: correction in hex_mic enum value

- picked improper snd device based on hex_mic enum value

- Modified hex_mic enum value to pick proper snd device

Change-Id: Ifbb3b4a658a9d8f0ef54dd963985827c47a35dd6
diff --git a/hal/msm8974/platform.h b/hal/msm8974/platform.h
index 1535940..089e437 100644
--- a/hal/msm8974/platform.h
+++ b/hal/msm8974/platform.h
@@ -42,7 +42,7 @@
     SOURCE_DUAL_MIC  = 0x2,            /* Target contains 2 mics */
     SOURCE_THREE_MIC = 0x4,            /* Target contains 3 mics */
     SOURCE_QUAD_MIC  = 0x8,            /* Target contains 4 mics */
-    SOURCE_HEX_MIC   = 0x16,           /* Target contains 6 mics */
+    SOURCE_HEX_MIC   = 0x10,           /* Target contains 6 mics */
     SOURCE_OCT_MIC   = 0x20,           /* Target contains 8 mics */
     SOURCE_DEC_MIC   = 0x40,
 };