mlxsw: spectrum_acl: Avoid size check for RX_ACL_SYSTEM_PORT element

RX_ACL_SYSTEM_PORT is 8 bit but SRC_SYS_PORT is 16 bits. Internally,
SRC_SYS_PORT is used to carry the value. Relax the checker in case of
RX_ACL_SYSTEM_PORT and allow different size.

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>