watchdog: Add reset support for OcteonTX / TX2

Adds support for Core 0 watchdog poke on OcteonTX and OcteonTX2
platforms.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>