ofp-util: Allow out-of-range indexes in ofputil_decode_geneve_table_reply().

Otherwise, if some future version of OVS supports more Geneve options than
the current version, and any of these extras are in use, then one would be
unable to dump them with "ovs-ofctl dump-geneve-map", and any other
OVS-based software that wants to dump the Geneve map to work with the
existing options (i.e. ovn-controller) would fail entirely, instead of
being able to work with at least a subset.

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