watchdog: s3c2410: Make reset disable register optional

On new Exynos chips (e.g. Exynos850 and Exynos9) the
AUTOMATIC_WDT_RESET_DISABLE register was removed, and its value can be
thought of as "always 0x0". Add correspondig quirk bit, so that the
driver can omit accessing it if it's not present.

This commit doesn't bring any functional change to existing devices, but
merely provides an infrastructure for upcoming chips support.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211107202943.8859-6-semen.protsenko@linaro.org


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