mlxsw: core_acl: Change order of args of ops->encode_block()

Change order so it is aligned with the usual case where the "write_to"
buffer comes as the first arg.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>