If the driver is not configured for `no way out`,
then the open method should not automatically allow
the setting of allow_close to CLOSE_STATE_ALLOW.

The setting of allow_close nullifies the use of
the magic close via the write path. It means that
in the default state, the watchdog will shut-down
even if the magic close has not been issued.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>