Remove GetMotionProc from ValuatorClassRec.

With the MD/SD device hierarchy we need control over the generation of the
motion history as well as the conversion later before posting it to the
client. So let's not let the drivers change it.

No x.org driver currently uses it anyway, linuxwacom doesn't either so dumping
it seems safe enough.

Xi/gtmotion.c

@@ -137,9 +137,9 @@ ProcXGetDeviceMotionEvents(ClientPtr client)
 	coords = (INT32 *) xalloc(tsize);
 	if (!coords)
 	    return BadAlloc;
-	rep.nEvents = (v->GetMotionProc) (dev, (xTimecoord *) coords,	/* XXX */
-					  start.milliseconds, stop.milliseconds,
-					  (ScreenPtr) NULL);
+	rep.nEvents = GetMotionHistory(dev, (xTimecoord *) coords,/* XXX */
+					start.milliseconds, stop.milliseconds,
+					(ScreenPtr) NULL);
     }
     if (rep.nEvents > 0) {
 	length = (rep.nEvents * size + 3) >> 2;