watchdog: loongson1: Add Loongson-2k0300 watchdog support

watchdog: loongson1: Add Loongson-2k0300 watchdog support

According to the manual, the Loongson-2K0300 watchdog is similar to the
Loongson-1, except for some register offsets and inconsistent register
bit definitions. Separate definitions via driver_data suffice.

Co-developed-by: Xiaochuang Mao <maoxiaochuan@loongson.cn>
Signed-off-by: Xiaochuang Mao <maoxiaochuan@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
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>