PCI paths of the WLAN devices have changed between kernel 4.4 and 4.9;
migrate config so existing wifi-iface definitions don't break.
This is implemented as a hotplug handler rather than a uci-defaults script
as the migration script must run before the 10-wifi-detect hotplug handler.
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
