s390/bpf: Fix skb_copy_bits() parameter passing

The skb_copy_bits() function has the following signature:
int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)

Currently in bpf_jit.S the "to" and "len" parameters have been
exchanged. So fix this and call the function with the correct
parameters.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>