xfrm: Fix bucket count reported to userspace

xfrm: Fix bucket count reported to userspace

BugLink: https://bugs.launchpad.net/bugs/1837477
[ Upstream commit ca92e173ab34a4f7fc4128bd372bd96f1af6f507 ]

sadhcnt is reported by `ip -s xfrm state count` as "buckets count", not the
hash mask.

Fixes: 28d8909bc790 ("[XFRM]: Export SAD info.")
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>