Return error code in a EC host command response

The caller of cros_ec_command_dev_v2 needs to know whether the
command was succesful or not. This change makes it return the
error code returned by the EC.

BUG=none
BRANCH=none
TEST=Run commands on Electro:
localhost ~ # /tmp/mosys ec pdchipinfo 2
cros_ec_command_dev_v2: EC command failed: 0x3

Change-Id: I5329e2a718ce487585f1c24809b1646817f2fe3f
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/439865
2 files changed