watchdog: realtek-otto: add RTL9310 support

The RTL9310 SoC series has a watchdog timer identical to the already
supported SoCs. The peripheral is memory mapped at 0x18003260 and driven
by the Lexra bus clock.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/629e95e16c8dc812dc5a4ea34a2e2e1ff2faf88c.1656356377.git.sander@svanheule.net


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