libpayload: Add drivers for bg4cd

BUG=chrome-os-partner:32772
BRANCH=none
TEST=Built chromeos-bootimage
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

Change-Id: I15cb40532855c89f6fb959652a7e874897eb45bb
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 8f8419fe22cf39d827e566b8f4dbe0680e4106a1
Original-Change-Id: I97f2ac8ffc7232c7a6c6d40deb8a35630d3d62a7
Original-Reviewed-on: https://chromium-review.googlesource.com/222662
Original-Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>
Original-Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: http://review.coreboot.org/9360
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
4 files changed