tcp: do not drop syn_recv on all icmp reports

Petr Novopashenniy reported that ICMP redirects on SYN_RECV sockets
were leading to RST.

This is of course incorrect.

A specific list of ICMP messages should be able to drop a SYN_RECV.

For instance, a REDIRECT on SYN_RECV shall be ignored, as we do
not hold a dst per SYN_RECV pseudo request.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=111751
Fixes: 079096f1

 ("tcp/dccp: install syn_recv requests into ehash table")
Reported-by: Petr Novopashenniy <pety@rusnet.ru>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>