Fix VNDK Compilation Errors

VNDK restrictions doesn't includes standard headers by
default, add them explicitly.

Change-Id: Icafac6f07fcdf58fccaabde8d472509090fb3e6f
diff --git a/hal/msm8974/platform.c b/hal/msm8974/platform.c
index 8e377f1..18e36d6 100644
--- a/hal/msm8974/platform.c
+++ b/hal/msm8974/platform.c
@@ -36,6 +36,7 @@
 #include <cutils/str_parms.h>
 #include <audio_hw.h>
 #include <platform_api.h>
+#include <unistd.h>
 #include "platform.h"
 #include "audio_extn.h"
 #include "acdb.h"