netinet/if_ether.h: add ETH_P_CFM from linux v5.11

see

  linux commit fbaedb4129838252570410c65abb2036b5505cbd
  bridge: uapi: cfm: Added EtherType used by the CFM protocol.

include/netinet/if_ether.h

@@ -66,6 +66,7 @@
 #define ETH_P_1588	0x88F7
 #define ETH_P_NCSI	0x88F8
 #define ETH_P_PRP	0x88FB
+#define ETH_P_CFM	0x8902
 #define ETH_P_FCOE	0x8906
 #define ETH_P_TDLS	0x890D
 #define ETH_P_FIP	0x8914