dtoverlay: Rebase aliases in overlays like labels
dtoverlay: Rebase aliases in overlays like labels

Aliases and labels/symbols are stored in the same way - as path strings.
The overlay application code already knows how to rewrite exported
symbol paths so they are correct in the base DTB (rebasing), so use the
same logic to rebase aliases as they are applied.

raspberrypi/userland,raspberrypi/userland,raspberrypi/userland