foris: add patch to store three-level time zones

Fixes issue turris/foris/foris#185 (closed) in Turris OS 3.x release

Recently, someone on support deparment hit this issue and it is a simple patch, so why don't we have it in Turris OS 3.x release. :) This is not compile & run tested. @jpavlinec would you please take care of it?