tools: ynl: fix build on systems with old kernel headers

tools: ynl: fix build on systems with old kernel headers

The wireguard YNL conversion was missing the customary .deps entry.
NIPA doesn't catch this but my CentOS 9 system complains:

 wireguard-user.c:72:10: error: ‘WGALLOWEDIP_A_FLAGS’ undeclared here
 wireguard-user.c:58:67: error: parameter 1 (‘value’) has incomplete type
 58 | const char *wireguard_wgallowedip_flags_str(enum wgallowedip_flag value)
    |                                             ~~~~~~~~~~~~~~~~~~~~~~^~~~~

And similarly does Ubuntu 22.04.

One extra complication here is that we renamed the header guard,
so we need to compat with both old and new guard define.

Reviewed-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Link: https://patch.msgid.link/20251207013848.1692990-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>