add new user to i2c and plugdev groups and start sddm like we do with phosh

This MR contains a couple of small improvements.

Namely adding the users created with this package to the plugdev group, which is needed for certain functionality in at least plasma-mobile.

This MR will also add the users to the autologin group, which seems to be needed by at least nemomobile. Was requested here.

Merging this requires us to remove sddm.service from the arm-profiles in plasma-mobile and in plasma-mobile-dev.

This would ofcourse also need to go into the pinephonepro-post-install package.

PS: I did not update the checksums in the PKGBUILD, as it will depend on how much change we apply. So that needs to be updated afterwards.

Signed-off-by: Dan Johansen strit@manjaro.org