This patch adds a tcpdiag_entry struct and makes tcpdiag_bc_run use it
instead of a struct sock.  This will allow us to use tcpdiag_bc_run on
struct open_request in the next patch.

Please note that I've left the CONFIG_IPV6 defines in as to support
ipv6 modules we'll need to modularise tcpdiag itself.  I'll probably
do that after this is all fixed.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>