net: fix compile error of implicit declaration of skb_probe_transport_header

The commit 40893fd0(net: switch to use skb_probe_transport_header())
involes a new error accidently. When NET_SKBUFF_DATA_USES_OFFSE is
not enabled, below compile error happens:

  CC      net/packet/af_packet.o
  net/packet/af_packet.c: In function ‘packet_sendmsg_spkt’:
  net/packet/af_packet.c:1516:2: error: implicit declaration of function ‘skb_probe_transport_header’ [-Werror=implicit-function-declaration]
  cc1: some warnings being treated as errors
  make[2]: *** [net/packet/af_packet.o] Error 1
  make[1]: *** [net/packet] Error 2
  make: *** [net] Error 2

As it seems skb_probe_transport_header() is not related to
NET_SKBUFF_DATA_USES_OFFSE, we should move the definition of
skb_probe_transport_header() out of scope of
NET_SKBUFF_DATA_USES_OFFSE macro.

Cc: Jason Wang <jasowang@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: NYing Xue <ying.xue@windriver.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1560,19 +1560,6 @@ static inline void skb_set_transport_header(struct sk_buff *skb,
 	skb->transport_header += offset;
 }
 
-static inline void skb_probe_transport_header(struct sk_buff *skb,
-					      const int offset_hint)
-{
-	struct flow_keys keys;
-
-	if (skb_transport_header_was_set(skb))
-		return;
-	else if (skb_flow_dissect(skb, &keys))
-		skb_set_transport_header(skb, keys.thoff);
-	else
-		skb_set_transport_header(skb, offset_hint);
-}
-
 static inline unsigned char *skb_network_header(const struct sk_buff *skb)
 {
 	return skb->head + skb->network_header;
@@ -1716,6 +1703,19 @@ static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
 }
 #endif /* NET_SKBUFF_DATA_USES_OFFSET */
 
+static inline void skb_probe_transport_header(struct sk_buff *skb,
+					      const int offset_hint)
+{
+	struct flow_keys keys;
+
+	if (skb_transport_header_was_set(skb))
+		return;
+	else if (skb_flow_dissect(skb, &keys))
+		skb_set_transport_header(skb, keys.thoff);
+	else
+		skb_set_transport_header(skb, offset_hint);
+}
+
 static inline void skb_mac_header_rebuild(struct sk_buff *skb)
 {
 	if (skb_mac_header_was_set(skb)) {