[INET]: Fix potential kfree on vmalloc-ed area of request_sock_queue

[INET]: Fix potential kfree on vmalloc-ed area of request_sock_queue

The request_sock_queue's listen_opt is either vmalloc-ed or
kmalloc-ed depending on the number of table entries. Thus it
is expected to be handled properly on free, which is done in
the reqsk_queue_destroy().

However the error path in inet_csk_listen_start() calls
the lite version of reqsk_queue_destroy, called
__reqsk_queue_destroy, which calls the kfree unconditionally.

Fix this and move the __reqsk_queue_destroy into a .c file as
it looks too big to be inline.

As David also noticed, this is an error recovery path only,
so no locking is required and the lopt is known to be not NULL.

reqsk_queue_yank_listen_sk is also now only used in
net/core/request_sock.c so we should move it there too.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>