librem5: Update power mgmt rules

This syncs with what is shipped in PureOS. Without this the modem disappears from the bus rather quickly but it also tweaks some other aspects.

With this I (and a suitable PureOS or Mobian kernel) I can run plain Debian and have display, modem, charging, etc. As we have some mainline ucm config we even get some audio.

Most notably missing is redpine wifi (would be great to look into using the mainline driver)