Add driver for CMSDK (Cortex-M System Design Kit) APB WDOG. This device
uses NMI as interrupt hence it requires Runtime NMI (CONFIG_RUNTIME_NMI)
to be configured in the platform.
Tested with drivers/watchdog sample application.
Jira: ZEP-1300
Change-Id: Ib318047109af81e32060e80d456ef3873fd380ea
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@linaro.org>