Use %pf instead of %p to output the function's address and print the
protocol's name.

Before patch:

  <idle>-0     [000] 60144.542521: kfree_skb: skbaddr=de7b8240 protocol=2048 location=c1365429
  <idle>-0     [000] 60164.488153: kfree_skb: skbaddr=da66f900 protocol=2048 location=c1365429
  <idle>-0     [000] 60193.493933: kfree_skb: skbaddr=deaeb480 protocol=4 location=c134ec25
  <idle>-0     [000] 60253.118421: kfree_skb: skbaddr=de7c4900 protocol=4 location=c134ec25
          
After patch:

  <idle>-0     [000]   169.979205: kfree_skb: skbaddr=ceddc240 protocol=ETH_P_802_2 location=netif_receive_skb
  <idle>-0     [000]   172.587000: kfree_skb: skbaddr=ceddc300 protocol=ETH_P_802_2 location=netif_receive_skb
    ping-3391  [000]   192.109803: kfree_skb: skbaddr=ceddc900 protocol=ETH_P_IP location=icmp_rcv
    ping-3391  [000]   192.109902: kfree_skb: skbaddr=ceddc780 protocol=ETH_P_IP location=icmp_rcv

Changelog v1->v2:
Convert protocol from raw numeric to its name as Frederic's suggestion

Signed-off-by: Xiao Guangrong <redacted>
Acked-by: Frederic Weisbecker <redacted>
---
 include/trace/events/skb.h |   70 ++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 1e8fabb..2496060 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h

@@ -7,6 +7,71 @@
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM skb
 
+#define protocol_name(protocol) { protocol, #protocol }
+#define show_protocol_name(val)					\
+	__print_symbolic(val,					\