soc/intel/skylake: Fix SPI WP disable status check

Use SPI write protect disable bit from BIOS_CONTROL register
to check write protect status.

Change-Id: Ie79fb4e3e92a4ae777c5d501abbb44a732a9862a
Signed-off-by: Ravi Sarawadi <ravishankar.sarawadi@intel.com>
Reviewed-on: https://review.coreboot.org/21449
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
3 files changed