mb/google/kahlee/variants/grunt: Enable BayHub720 driver

Enable this driver along with power saving.

BUG=b:73726008
BRANCH=none
TEST=boot and see this message:
BayHub BH720: Power-saving enabled 110103
From linux:
$ iotools pci_read32 2 0 0 0x90
0x00110103

Change-Id: I850e923f73e01fe629d66ad61b65afa58035845c
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://review.coreboot.org/25967
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2 files changed