procd: adjust /dev entries to desktop distro defaults
This changes the default permissions for /dev entries to be more similar to
a desktop distro. Taken from the defaults of Arch Linux and Ubuntu. Also
changed some that were nonsensical. For example, all 660 permissions on
desktop distros were of the form root:x where x is something other than
root. As such, 660 is useless for LEDE where the specific group is missing.
audio seems to be the only group that isn't.
Signed-off by: Rosen Penev <rosenp@gmail.com>