ARM: dts: msm: add dt entry for watchdog absent register

There are two watchdog timers one per cluster but either can be used for
both clusters if the other is disabled. Add watchdog absent register dt
entry to disable watchdog for one of the clusters.

Change-Id: Iab4792d6c57175ea65030666a509152042579b79
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>