platform/chrome: cros_ec_trace: Add fields to command traces

In ftrace, add more fields to the cros_ec command event:

  - Add size of commands to check if they are properly set.
  - Add offset (in case an EC is cascaded being another EC),
    to allow proper command output

With:

  echo 1 > events/cros_ec/cros_ec_cmd/enable

We now have (on samus)

Invalid command for the sensor stack:

  ectool-6942  [002] ....  3082.783116: cros_ec_request_done: version: 3,
  offset: 0, command: EC_CMD_MOTION_SENSE_CMD, outsize: 2, insize: 19,
  ec result: EC_RES_INVALID_PARAM, retval: 0

Powerd accessing PD EC being the main EC:

  powerd-1272  [002] ....    40.644026: cros_ec_request_done: version: 0,
  offset: 1, command: EC_CMD_USB_PD_POWER_INFO, outsize: 1, insize: 16,
  ec result: EC_RES_SUCCESS, retval: 16

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Acked-by: Raul E Rangel <rrangel@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>