ipmr: Use on-device stats instead of private ones.

These devices use the private area of appropriate size for
statistics. Turning them to use on-device ones make them
"privless" and thus - really small wrt kmalloc cache, they
are allocated from.

Besides, code looks nicer, because of absence of multi-braced
type casts and dereferences.

[ Fix build failures -DaveM ]

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>