watchdog: sbsa: Set WDOG_HW_RUNNING, when watchdog is already running.

This patch uses the new flag WDOG_HW_RUNNING in driver.
According to the definition of this flag, it should be set,
if watchdog is running after booting, before it's opened.

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>