net: cls_u32: fix missed pcpu_success free_percpu

This fixes a missed free_percpu in the unwind code path and when
keys are destroyed.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>