watchdog: f71808e: maintain watchdog timeout occurred flag ...

If we experience a watchdog reset, the indicating flag should persist
till the Linux driver had a chance to see it.

The flag bit is special however in that writing 1 clears the bit and
writing 0 keeps it intact, i.e. :

Bit
read written  result
  0     0     = 0
  1     0     = 1
  0     1     = 0
  1     1     = 0

So in the bootloader, we should write a zero always. The OS on the
other hand can either write 1 or the old value after reading to
clear the flag.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: f71808e: only print reset reason if one's indicated ...

On most resets, a "reset reason: unknown" would clutter the console,
because the watchdog doesn't support differentiating between POR and
RST. Reduce the clutter by only printing the message when we have
something interesting to say (i.e. watchdog reset).

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: f71808e: support .running device parameter ...

The American Megatrends BIOS I am using can be configured to start the
Fintek watchdog prior to the UEFI payloads. To avoid BIOS updates that reset
this functionality going unnoticed, implement support for WDOG_HW_RUNNING.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

watchdog: add support for Fintek F718xx and, F818xx Super I/O ...

This is an adaptation of the Linux v5.3 f71808e_wdt driver for the watchdog
component of the Fintek Super I/O chips.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>