rules: Fix persistent input symlinks for interface 00

rules: Fix persistent input symlinks for interface 00

Commits 5e9eb156c and 32567f8 introduced persistent symlinks for input devices
with more than one interface. However, this does not ensure stability for the
"default" interface, i. e. with interface number 00 or a nonexisting one. If a
device with a higher interface number appears first, it'll claim the symlink
name without an interface number, and the "interface 00" device won't get any.

Fix this by creating the default symlink only for interface 00 or a nonexisting
one, so that we properly partition the two cases over the two rules.

https://launchpad.net/bugs/1057824