base-defaults: disable system suspend (and hibernation) in systemd

deep sleep / suspend to ram is not yet available (via ATF/uboot) so will take us a while to support.

s2idle ("freeze") is the prerequirement and what we're working towards in the kernel. Until that at least does not cleanly resume, configure systemd not to do system suspend at all.

This fixes users suspending the system (via a GUI) and having to reset the phone manually, since now suspend to ram is configured.

Also, the configuration for s2idle is prepared so that it's obvious what our goal is now.