spi: sprd: adi: Add a reset reason for watchdog mode

spi: sprd: adi: Add a reset reason for watchdog mode

When the system was rebooted by watchdog, now we did not save the watchdog
reset mode which will make system enter a incorrect mode after rebooting.

Thus we should set the watchdog reset mode as default when opening the
watchdog configuration, that means if the system was rebooted by other
reason through the restart_handler(), then we will clear the default
watchdog reset mode to save the correct reset mode.

Signed-off-by: Sherry Zong <sherry.zong@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Link: https://lore.kernel.org/r/1563f3de43c6c2262d597a25d6138b5de61ea23d.1564125131.git.baolin.wang@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>