hw/arm_timer.c: Fix bounds check for Integrator timer accesses

There are only three counter/timers on the integrator board:
correct the bounds check to avoid an array overrun. (Spotted
by Coverity, see bug 887883).
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/arm_timer.c

@@ -269,7 +269,7 @@ static uint64_t icp_pit_read(void *opaque, target_phys_addr_t offset,
 
     /* ??? Don't know the PrimeCell ID for this device.  */
     n = offset >> 8;
-    if (n > 3) {
+    if (n > 2) {
         hw_error("sp804_read: Bad timer %d\n", n);
     }
 
@@ -283,7 +283,7 @@ static void icp_pit_write(void *opaque, target_phys_addr_t offset,
     int n;
 
     n = offset >> 8;
-    if (n > 3) {
+    if (n > 2) {
         hw_error("sp804_write: Bad timer %d\n", n);
     }