watchdog: ixp4xx: Make sure restart always works

stable inclusion
from stable-v6.6.2
commit deedc3e1e98e4e5082928fc21ebd5e8604a2d3d6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8IW7G

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=deedc3e1e98e4e5082928fc21ebd5e8604a2d3d6



--------------------------------

[ Upstream commit b4075ecfe348a44209534c75ad72392c63a489a6 ]

The IXP4xx watchdog in early "A0" silicon is unreliable and
cannot be registered, however for some systems such as the
USRobotics USR8200 the watchdog is the only restart option,
so implement a "dummy" watchdog that can only support restart
in this case.

Fixes: 1aea5228 ("watchdog: ixp4xx: Implement restart")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230926-ixp4xx-wdt-restart-v2-1-15cf4639b423@linaro.org


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>