[NETFILTER]: Remove some EXPERIMENTAL dependencies

Most of the netfilter modules are not considered experimental anymore,
the only ones I want to keep marked as EXPERIMENTAL are:

- TCPOPTSTRIP target, which is brand new.

- SANE helper, which is quite new.

- CLUSTERIP target, which I believe hasn't had much testing despite
  being in the kernel for quite a long time.

- SCTP match and conntrack protocol, which are a mess and need to
  be reviewed and cleaned up before I would trust them.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>