Querying link info for the GTP interface doesn't reveal in which "role" the
device is set to operate.  Include this information in the info query
result.
Signed-off-by: NJonas Bonn <jonas@norrbonn.se>
Acked-by: NHarald Welte <laforge@gnumonks.org>
Acked-by: NPravin B Shelar <pshelar@ovn.org>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>