watchdog: jz4740: Use register names from <linux/mfd/ingenic-tcu.h>

Use the macros from <linux/mfd/ingenic-tcu.h> instead of declaring our
own.

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