mediatek: Share watchdog timer code among similar SOCs

Refactor watchdog timer (WDT) code which will be reused among similar
SOCs.

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

Change-Id: I745c2f204924d9eee1941c0f3e9b6ba45cfb1958
Signed-off-by: Tristan Shieh <tristan.shieh@mediatek.com>
Reviewed-on: https://review.coreboot.org/27024
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed