sock: fix error in sock_setsockopt()

Some tests are failing, John bisected the issue to a recent commit.

sock_set_timestamp() parameters should be :

1) sk
2) optname
3) valbool

Fixes: 371087aa ("sock: expose so_timestamp options for mptcp")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Bisected-by: John Sperbeck <jsperbeck@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Mat Martineau <mathew.j.martineau@linux.intel.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>