net: openvswitch: add missing .resv_start_op

I missed one of the families in OvS when annotating .resv_start_op.
This triggers the warning added in commit ce48ebdd ("genetlink:
limit the use of validation workarounds to old ops").

Reported-by:  <syzbot+40eb8c0447c0e47a7e9b@syzkaller.appspotmail.com>
Fixes: 9c5d03d3 ("genetlink: start to validate reserved header bytes")
Link: https://lore.kernel.org/r/20221028032501.2724270-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>