ARM: dts: qcom: Add dt-node for msm watchdog

Watchdog driver detects hangs/freezes in the system. If the watchdog
is not "pet" at regular intervals, the system is assumed to have
become non responsive and is reset. Add device tree entry for the
watchdog timer driver.

Change-Id: Ie9276a36b8ad9532c411920bf8c32b7fa4752f00
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>