Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/marvell/mvpp2/mvpp2_cls.c: In function 'mvpp2_cls_c2_build_match':
drivers/net/ethernet/marvell/mvpp2/mvpp2_cls.c:1159:28: warning:
 variable 'act' set but not used [-Wunused-but-set-variable]

It is never used since introduction in
commit 90b509b3 ("net: mvpp2: cls: Add Classification offload support")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>