Move test utilities to common directory, and use them more widely.

Change-Id: Ib7397eccf811fec6a746254a613936c8466ac9e6
diff --git a/test/vmapi/primary_with_secondaries/mailbox.c b/test/vmapi/primary_with_secondaries/mailbox.c
index f08c696..c58115a 100644
--- a/test/vmapi/primary_with_secondaries/mailbox.c
+++ b/test/vmapi/primary_with_secondaries/mailbox.c
@@ -23,7 +23,7 @@
 
 #include "primary_with_secondary.h"
 #include "test/hftest.h"
-#include "util.h"
+#include "test/vmapi/spci.h"
 
 /**
  * Reverses the order of the elements in the given array.