watchdog: octeon-wdt: Add support for 78XX SOCs.

Signed-off-by: Carlos Munoz <carlos.munoz@caviumnetworks.com>
Signed-off-by: Steven J. Hill <steven.hill@cavium.com>
Acked-by: David Daney <david.daney@cavium.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Cc: linux-mips@linux-mips.org
Cc: linux-watchdog@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17214/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>