[INET]: Consolidate inet(6)_hash_connect.

These two functions are the same except for what they call
to "check_established" and "hash" for a socket.

This saves half-a-kilo for ipv4 and ipv6.

 add/remove: 1/0 grow/shrink: 1/4 up/down: 582/-1128 (-546)
 function                                     old     new   delta
 __inet_hash_connect                            -     577    +577
 arp_ignore                                   108     113      +5
 static.hint                                    8       4      -4
 rt_worker_func                               376     372      -4
 inet6_hash_connect                           584      25    -559
 inet_hash_connect                            586      25    -561

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>