soc/intel/skylake: use SPI flash boot_device_rw() for ealy stages
If the boot device is SPI flash use the common one in the
early stages. While tweaking the config don't auto select
SPI_FLASH as that is handled automatically by the rest of the
build system.
BUG=chrome-os-partner:56151
Change-Id: Ifd51a80fd008c336233d6e460c354190fcc0ef22
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16202
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>