net: openvswitch: Constify static struct genl_small_ops

The only usage of these is to assign their address to the small_ops field
in the genl_family struct, which is a const pointer, and applying
ARRAY_SIZE() on them. Make them const to allow the compiler to put them
in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>