net: mvpp2: cls: Use the correct number of rules in various places

As of today, the classification offload implementation only supports 4
different rules to be offloaded. This number has been hardcoded in the
rule insertion function, and the wrong define is being used elsewhere.

Use the correct #define everywhere to make sure we always check for the
correct number of rules.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>