watchdog: sbsa: Use max_hw_heartbeat_ms instead of max_timeout

Using max_hw_heartbeat_ms instead of max_timeout gives the flexibility to
achieve higher user "timeout". Therefore, use this new infrastructure.

Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Fu Wei <fu.wei@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>