netlink: specs: rt-link: fix ifinfo-flags names

Correct the names of `enum net_device_flags` constants:

- IFF_POINTOPOINT should be "pointopoint", not "point-to-point".
- IFF_NOTRAILERS should be "notrailers", not "no-trailers".
- IFF_NOARP should be "noarp", not "no-arp".
- IFF_ALLMULTI should be "allmulti", not "all-multi".
- IFF_AUTOMEDIA should be "automedia", not "auto-media".

Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260925213918.204767-4-ast@fiberby.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>