This new command is missing.

Fixes: 880a6fab ("xfrm: configure policy hash table thresholds by netlink")
Reported-by: NChristophe Gouault <christophe.gouault@6wind.com>
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>