mainboard/google/reef: add snappy variant

Create the initial Snappy variant which refers to the Reef device.

Snappy, an Apollolake-platform, is deviated from reference board Reef.

BRANCH=master
BUG=None
TEST=Built & booted

Signed-off-by: Wisley Chen <wisley.chen@quantatw.com>
Change-Id: I6f32c0b1a154edbd8c4822acdbdbdbeb4a0098e6
Reviewed-on: https://review.coreboot.org/17043
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
6 files changed