mlxsw: spectrum_acl: Ignore always-zeroed bits in tp->prio

The lowest 16 bits of tp->prio are always zero, so ignore them with a
shift.

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>