Add a missing VMSTATE_TIMER() entry to the arm_mptimer vmstate
description; this omission meant that we would probably hang on reload
when the timer failed to fire.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 1363967348-3044-1-git-send-email-peter.maydell@linaro.org