tcp: rename tcp_skb_cb flags

Rename struct tcp_skb_cb "flags" to "tcp_flags" to ease code review and
maintenance.

Its content is a combination of FIN/SYN/RST/PSH/ACK/URG/ECE/CWR flags

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index cc0d5de..131c45f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -524,7 +524,7 @@
 
 static inline void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb)
 {
-	TCP_SKB_CB(skb)->flags |= TCPHDR_PSH;
+	TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
 	tp->pushed_seq = tp->write_seq;
 }
 
@@ -540,7 +540,7 @@
 
 	skb->csum    = 0;
 	tcb->seq     = tcb->end_seq = tp->write_seq;
-	tcb->flags   = TCPHDR_ACK;
+	tcb->tcp_flags = TCPHDR_ACK;
 	tcb->sacked  = 0;
 	skb_header_release(skb);
 	tcp_add_write_queue_tail(sk, skb);
@@ -830,7 +830,7 @@
 		skb_shinfo(skb)->gso_segs = 0;
 
 		if (!copied)
-			TCP_SKB_CB(skb)->flags &= ~TCPHDR_PSH;
+			TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
 
 		copied += copy;
 		poffset += copy;
@@ -1074,7 +1074,7 @@
 			}
 
 			if (!copied)
-				TCP_SKB_CB(skb)->flags &= ~TCPHDR_PSH;
+				TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
 
 			tp->write_seq += copy;
 			TCP_SKB_CB(skb)->end_seq += copy;