openflow: Add additional reserved space in struct nx_geneve_table_reply.

openflow: Add additional reserved space in struct nx_geneve_table_reply.

It's possible to imagine that a switch might want to report additional
capabilities related to Geneve beyond just the number of options and
how much space they can consume. Some examples include additional
restrictions on parsing (if this command is used for non-OVS implementations
or OVS changes how it works) and per-packet actions that can't be done
generically (such as checksums or encryption). It's not yet clear if
these will be necessary or if OpenFlow is the right place to expose
them. However, it's easy to do now and there is very little cost so
it seems like a good idea to leave some additional reserved space.

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