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/include/net/sock.h b/include/net/sock.h
index 08f05f9..5c97b0f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2159,10 +2159,9 @@
  * @sk:		socket sending this packet
  * @tx_flags:	filled with instructions for time stamping
  *
- * Currently only depends on SOCK_TIMESTAMPING* flags. Returns error code if
- * parameters are invalid.
+ * Currently only depends on SOCK_TIMESTAMPING* flags.
  */
-extern int sock_tx_timestamp(struct sock *sk, __u8 *tx_flags);
+extern void sock_tx_timestamp(struct sock *sk, __u8 *tx_flags);
 
 /**
  * sk_eat_skb - Release a skb if it is no longer needed