arm64: dts: librem5: Don't use kill switches as keys

Using them as keys has several problems:

• the pressed state can trigger auto repeat in other parts of the stack
• userspace expects the switches to mean 'toggle' not 'indicate'. So flipping e.g. the wifi killswitch toggles airplane mode although it should indicate: hks engaged.

This closes OS-issues#178 (closed). However I still have the issue that the modem stays disabled after entering the pin.

The full fix needs a rfkill/privacy driver (since e.g. audio is not RF) for the wifi/wwan/audio parts (see !77 (closed))

Note that the code is not upsteam (for good reason).

EDIT: Librem5/debs/ModemManager#15 (comment 69997) has the hint how to reenable the modem permanently again.