[NET_SCHED]: sch_ingress: avoid a few #ifdefs

Move the repeating "ifndef CONFIG_NET_CLS_ACT/ifdef CONFIG_NETFILTER"
ifdefs into a single condition.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>