docs: watchdog: codify ident.options as superset of possible status flags

docs: watchdog: codify ident.options as superset of possible status flags

The FIXME comment has been in-tree since the very first git commit.
The described behavior has been since relied on by some userspace, e.g.
the util-linux wdctl command and has been ignored by some kernelspace,
like the f71808e_wdt driver.

The functionality is useful to have to be able to differentiate between a
driver that doesn't support WDIOF_CARDRESET and one that does, but hasn't
had a watchdog reset, thus drop the FIXME to encourage drivers adopting
this convention.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200611191750.28096-2-a.fatoum@pengutronix.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>