[coreboot-gerrit] Patch merged into coreboot/master: Kconfig: introduce writable boot device notion

the following patch was just integrated into master:
commit e8e118dd324e32070a1550e3f8ff90dd6fad72f8
Author: Aaron Durbin 
Date:   Fri Aug 12 15:00:10 2016 -0500

Kconfig: introduce writable boot device notion

Indicate to the build system that a platform provides support
    for a writable boot device. The following will provide the
    necessary support:

COMMON_CBFS_SPI_WRAPPER users
    soc/intel/apollolake
    soc/intel/baytrail
    soc/intel/braswell
    soc/intel/broadwell
    soc/intel/skylake

The SPI_FLASH option is auto-selected if the platform provides
    write supoprt for the boot device and SPI flash is the boot
    device.

Other platforms may provide similar support, but they do that
    in a device specific manner such as selecting SPI_FLASH
    explicitly. This provides clearance against build failures
    where chipsets don't provide SPI API implementations even
    though the platform may use a SPI flash to boot.

BUG=chrome-os-partner:56151

Change-Id: If78160f231c8312a313f9b9753607d044345d274
    Signed-off-by: Aaron Durbin 
    Reviewed-on: https://review.coreboot.org/16211
    Reviewed-by: Furquan Shaikh 
    Tested-by: build bot (Jenkins)
    Reviewed-by: Paul Menzel 
    Reviewed-by: Martin Roth

See https://review.coreboot.org/16211 for details.

-gerrit