net-timestamp: only report sw timestamp if reporting bit is set

The timestamping API has separate bits for generating and reporting
timestamps. A software timestamp should only be reported for a packet
when the packet has the relevant generation flag (SKBTX_..) set
and the socket has reporting bit SOF_TIMESTAMPING_SOFTWARE set.

The second check was accidentally removed. Reinstitute the original
behavior.

Tested:
  Without this patch, Documentation/networking/txtimestamp reports
  timestamps regardless of whether SOF_TIMESTAMPING_SOFTWARE is set.
  After the patch, it only reports them when the flag is set.

Fixes: f24b9be5957b ("net-timestamp: extend SCM_TIMESTAMPING ancillary data struct")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/socket.c b/net/socket.c
index 95ee7d8..4eb09b3 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -734,8 +734,7 @@
 	}
 
 	memset(&tss, 0, sizeof(tss));
-	if ((sk->sk_tsflags & SOF_TIMESTAMPING_SOFTWARE ||
-	     skb_shinfo(skb)->tx_flags & SKBTX_ANY_SW_TSTAMP) &&
+	if ((sk->sk_tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
 	    ktime_to_timespec_cond(skb->tstamp, tss.ts + 0))
 		empty = 0;
 	if (shhwtstamps &&