main/postmarketos-base-ui: setup cgroups on boot (MR 4585)

Allows things like podman/docker to work out of the box.

I looked at /etc/init.d/cgroups, and having this service enabled isn't a
problem if the kernel doesn't have cgroup support... in that situation,
the service script just simply exits (success).

[ci:skip-build] already built successfully in CI

main/postmarketos-base-ui/APKBUILD

 # Maintainer: Clayton Craft <clayton@craftyguy.net>
 pkgname=postmarketos-base-ui
-pkgver=14
+pkgver=15
 pkgrel=0
 pkgdesc="Meta package for minimal postmarketOS UI base"
 url="https://postmarketos.org"

main/postmarketos-base-ui/postmarketos-base-ui.post-install

 #!/bin/sh -e
 
-for service in dbus haveged wpa_supplicant chronyd rfkill; do
+for service in cgroups dbus haveged wpa_supplicant chronyd rfkill; do
 	rc-update -q add $service default
 done
 exit 0