The post-upgrade script in pmos-base isn't symlinked to the post-install
script, so zram-init wasn't being enabled on systems that upgraded to
the pmos-base version that intro'd this feature. I think this should
have been enabled by default on upgraded systems. There's a deviceinfo
toggle for it, so users who won't want to use this can set that var to
disable it, in that case having the service enabled is basically a
no-op.

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