arm/dt: msm9625: Add modem subsystem support

The modem on the msm9625 reports errors via a watchdog
interrupt and via the SMSM callback mechanism. Add support
to monitor these errors and invoke subsystem restart in
case the modem crashes.

Change-Id: I085b4e000c6a9bb23ad3de4df8c8d55424d6ecd4
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>