Don't release unlocked sock.

When user builds IPv6 header and send it through raw socket, kernel
tries to release unlocked sock. (Kernel log shows
"BUG: bad unlock balance detected" with enabled debug option.)

The lock is held only for non-hdrincl sock in this function
then this patch fix to do nothing about lock for hdrincl one.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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