Add AID for CrOS EC

Add AID for CrOS EC. The AID will be used to update the file access
permissions for /dev/cros_ec. This file is accessed by various
tools/daemons/services that interact with the Embedded Controller via
the linux kernel ChromeOS Embedded Controller (cros_ec) driver.

Bug: 349695348
Test: $ adb shell id -u cros_ec
Test: $ adb shell id -g cros_ec
Change-Id: I6baca9d2b63c45823ed5529bf27b904bf67edf8b