ARM: dts: dra7-evm: Add watchdog timers for IPU2

The watchdog timer information has been added to the IPU2 remote
processor device node on DRA7 EVM board. The watchdog functionality
will use GPTimers 4 and 9 for each of the cores in IPU2. No watchdog
timer is added to the remaining IPU and DSP processors, but can be
easily added as per need.

The MPU-side drivers will use this data to initialize the watchdog
timers, and listen for any watchdog triggers. The BIOS-side code on
IPU2 needs to configure/refresh this timer properly to not throw a
watchdog error.

Signed-off-by: Suman Anna <s-anna@ti.com>