XF86VidMode: Fix free() on walked pointer

Based on: https://patchwork.freedesktop.org/patch/85636/

Rewritten to just not walk the pointer.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Emi Velikov <emil.l.velikov@gmail.com>

Xext/vidmode.c

@@ -1364,7 +1364,7 @@ ProcVidModeGetDotClocks(ClientPtr client)
     WriteToClient(client, sizeof(xXF86VidModeGetDotClocksReply), &rep);
     if (!ClockProg) {
         for (n = 0; n < numClocks; n++) {
-            dotclock = *Clocks++;
+            dotclock = Clocks[n];
             if (client->swapped) {
                 WriteSwappedDataToClient(client, 4, (char *) &dotclock);
             }