udp: use EXPORT_IPV6_MOD[_GPL]()

udp: use EXPORT_IPV6_MOD[_GPL]()

Use EXPORT_IPV6_MOD[_GPL]() for symbols that don't need
to be exported unless CONFIG_IPV6=m

udp_table is no longer used from any modules, and does not
need to be exported anyway.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Mateusz Polchlopek <mateusz.polchlopek@intel.com>
Link: https://patch.msgid.link/20250212132418.1524422-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>