mediatek: Move watchdog timer code to a common directory

Move watchdog timer (WDT) code which can be reused into a common
directory under soc/mediatek.

BUG=b:80501386
BRANCH=none
TEST=Boots correctly on Elm

Change-Id: Icbeb04f775c3c0fdc18dd198df8591f5c4b6ddce
Signed-off-by: Tristan Shieh <tristan.shieh@mediatek.com>
Reviewed-on: https://review.coreboot.org/27025
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
3 files changed