Move RPS config to site.pp where it belongs.

The interface list is already hardware-specific (we weren't
hitting eth1-3 in eqiad), and will become moreso with RSS, and
this more closely aligns with where we've placed other hardware
network hacks like GRO/LRO disable.

Change-Id: I62e19c3c1e9552400a21c7afaa79396e60aa67eb