target-arm: fix sorting issue of KVM cpreg list

The compare_u64 function was not sorting the KVM cpreg_list in the
right way due to the wrong returned value.  Since we are comparing
two 64bit values we can't simply return their difference if the
returned type is int.
Signed-off-by: NAlvise Rigo <a.rigo@virtualopensystems.com>
Message-id: 1381513125-26802-2-git-send-email-a.rigo@virtualopensystems.com
[PMM: fixed coding style, indent and commit message formatting]
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/kvm.c

@@ -67,7 +67,13 @@ static bool reg_syncs_via_tuple_list(uint64_t regidx)
 
 static int compare_u64(const void *a, const void *b)
 {
-    return *(uint64_t *)a - *(uint64_t *)b;
+    if (*(uint64_t *)a > *(uint64_t *)b) {
+        return 1;
+    }
+    if (*(uint64_t *)a < *(uint64_t *)b) {
+        return -1;
+    }
+    return 0;
 }
 
 int kvm_arch_init_vcpu(CPUState *cs)