os-release.d: Add system_id.

This is the app id of the SoM stored in the system.

Test: adb shell cat /etc/os-release.d/system_id
Change-Id: Iba7ac028ffa7402f06fbf9c4a3a077eb3414940e
(cherry picked from commit d41148b6c8d59d4f35711028248fc644428ddc57)
1 file changed