watchdog: w83627hf_wdt: add bootstatus support

The status bit in the status and control register can tell us whether
the last reboot was caused by the watchdog. Make sure to take that into
the bootstatus before clearing it.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220824152448.7736-1-henning.schild@siemens.com


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