spi: sprd: adi: Add a reset reason for factory test mode

Add a new reset flag to indicate that the system need enter factory test
mode after restarting system.

Signed-off-by: Sherry Zong <sherry.zong@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Link: https://lore.kernel.org/r/8ae5651e876b527920ff878721a8a8ef47b099ac.1564125131.git.baolin.wang@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>