net: sock: make sock_tx_timestamp void

Currently, sock_tx_timestamp() always returns 0. The comment that
describes the sock_tx_timestamp() function wrongly says that it
returns an error when an invalid argument is passed (from commit
20d4947353be, ``net: socket infrastructure for SO_TIMESTAMPING'').
Make the function void, so that we can also remove all the unneeded
if conditions that check for such a _non-existant_ error case in the
output path.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/can/raw.c b/net/can/raw.c
index c1764e4..1085e65 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -711,9 +711,8 @@
 	err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
 	if (err < 0)
 		goto free_skb;
-	err = sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
-	if (err < 0)
-		goto free_skb;
+
+	sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
 
 	skb->dev = dev;
 	skb->sk  = sk;