Rename shutdown() to power_off() to avoid conflicts with libc for tests.

Change-Id: I1b8a61ad93294d296d711ff8a2f2c2c597b991e3
diff --git a/test/hftest/hftest.c b/test/hftest/hftest.c
index 1016a9a..1193407 100644
--- a/test/hftest/hftest.c
+++ b/test/hftest/hftest.c
@@ -93,7 +93,7 @@
 static noreturn void abort(void)
 {
 	HFTEST_LOG("FAIL");
-	shutdown();
+	arch_power_off();
 }
 
 static void run_test(hftest_test_fn set_up, hftest_test_fn test,