CHROMIUM: mfd: chromeos_ec: add I2C pass-through and other firmware bits

CHROMIUM: mfd: chromeos_ec: add I2C pass-through and other firmware bits

Add an I2C adapter acting as a pass-through to send firmware update EC
commands from userspace (e.g. flashrom).
Also add sysfs nodes to get firmware version and other EC info.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=chrome-os-partner:8865
TEST=on Daisy, run flashrom -p internal:bus=lpc -w ec.bin

Change-Id: Ib58b183da0e6c79d17689e057b24aae961fdd128
Reviewed-on: https://gerrit-int.chromium.org/17856
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>