Fix VNDK Compilation Errors

VNDK restrictions enforces AOSP headers to be referenced
through header library. Reference hardware header library
for 'hardware/hardware.h'.

Change-Id: Ia6abf3e9fedfa373be09c42c62b1860d8115019e
diff --git a/Android.mk b/Android.mk
index a522d56..c8725dd 100644
--- a/Android.mk
+++ b/Android.mk
@@ -36,7 +36,7 @@
 LOCAL_SRC_FILES := thermal-default.c
 endif
 
-LOCAL_HEADER_LIBRARIES := libutils_headers
+LOCAL_HEADER_LIBRARIES := libutils_headers libhardware_headers
 LOCAL_SHARED_LIBRARIES := liblog libcutils
 LOCAL_MODULE_TAGS := optional
 LOCAL_CFLAGS := -Wno-unused-parameter