drivers/watchdog: Add support for Microchip XEC device

Such watchdog timer is found on mec1501.
It comes with a support of dbg stall feature and interrupt support.

It does not support multistaging.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
Signed-off-by: Daniel Leung <daniel.leung@intel.com>