datapath: Drop datapath index and port number from Ethtool output.

datapath: Drop datapath index and port number from Ethtool output.

I introduced this a long time ago as an efficient way for userspace to find
out whether and where an internal device was attached, but I've always
considered it an ugly kluge.  Now that ODP_VPORT_QUERY can fetch a vport's
info regardless of datapath, it is no longer necessary.  This commit
stops using Ethtool for this purpose and drops the feature.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>