baytrail: romstage: Add config option to enable RMT

Add config option to enable RMT in the MRC.

BUG=chrome-os-partner:21807
TEST=Manual. Build w/ "USE=rmt", verify RMT print seen on FW console.
Build w/o USE flag, verify no RMT print.
BRANCH=None.
CQ-DEPEND=CL:*148655

Change-Id: Ibd3da87317a3359e797d9b43bc437e7227a85048
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/178095
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4982
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
3 files changed