gru: Enable EC-based RTC

Obtain the real-time clock value from the EC on start-up and show the
current time.

BUG=chrome-os-partner:52220
BRANCH=none
TEST=(partial) with future commits and EC clock set, boot on gru into
      Linux shell and check the firmware log:

      localhost ~ # grep Date: /sys/firmware/log
      Date: 2016-06-20 (Monday)  Time: 18:09:16

Change-Id: Id3ef791f546419c4881a891251cbb62d7596884b
Signed-off-by: Martin Roth <martinroth@chromium.org>
Original-Commit-Id: 348e9373b0e95a17f5c39ec28a480712e6e45caf
Original-Change-Id: Iff43b16a86d9fee483420ee2eff5ff3d276716a3
Original-Signed-off-by: Simon Glass <sjg@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/351781
Original-Commit-Ready: Vadim Bendebury <vbendeb@chromium.org>
Original-Tested-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/15303
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
1 file changed