netfilter: include/linux/netfilter/nf_conntrack_tuple_common.h: Checkpatch cleanup

include/linux/netfilter/nf_conntrack_tuple_common.h:5: ERROR: open brace '{' following enum go on the same line

Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>