dix: plug memory leak in freeing TouchClass

==15562== 1,800 bytes in 1 blocks are definitely lost in loss record 298 of 330
==15562==    at 0x4A06B6F: calloc (vg_replace_malloc.c:593)
==15562==    by 0x4312C7: InitTouchClassDeviceStruct (devices.c:1644)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>

dix/devices.c

@@ -795,6 +795,7 @@ FreeDeviceClass(int type, pointer *class)
             free((*t)->touches[i].valuators);
         }
 
+        free((*t)->touches);
         free((*t));
         break;
     }