Long story short, makedev is used by buildroot to fix up file or directory permissions directly in the generated image. However makedev doesn't seem to take well to file names containing spaces. This commit fixes this problem by changing the file name and also the connection name itself, from NetworkManager's viewpoint.

The default setting for generating addresses in IPv6 with NetworkManager is stable-privacy. That makes for unpredictable IPv6 addresses accross slots, and is hence entirely inacceptable. This commit changes this to be standard SLAAC without privacy instead. This also adds a device table to set the correct file permissions for the provided nmconnection file (0600 is required).