flapjack: Fork board.h/board.c from kukui

BUG=none
BRANCH=none
TEST=BOOTBLOCK=... make BOARD=flapjack -j flash_ec; and see AP boots.

Change-Id: Ieea89948598e51d8d4623c9d761d8ef8e7c546b2
Signed-off-by: Kaka Ni <nigang@huaqin.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/1445956
Reviewed-by: Nick Sanders <nsanders@chromium.org>