watchdog: bcm7038_wdt: add big endian support

bcm7038_wdt can be used on bmips big endian (bcm63xx) devices too.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210223080042.29569-1-noltari@gmail.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>