platform/chrome: cros_ec_proto: separate cros_ec_wait_until_complete()

EC returns EC_RES_IN_PROGRESS if the host command needs more time to
complete.  Whenever receives the return code, cros_ec_send_command()
sends EC_CMD_GET_COMMS_STATUS to query the command status.

Separate cros_ec_wait_until_complete() from cros_ec_send_command().
It sends EC_CMD_GET_COMMS_STATUS and waits until the previous command
was completed, or encountered error, or timed out.

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20220718050914.2267370-7-tzungbi@kernel.org