if_ether.h: add EtherCAT Ethertype

Add the Ethertype for EtherCAT protocol.
Signed-off-by: Daniel Braunwarth <daniel@braunwarth.dev>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/uapi/linux/if_ether.h

@@ -89,6 +89,7 @@
 #define ETH_P_PROFINET	0x8892		/* PROFINET			*/
 #define ETH_P_REALTEK	0x8899          /* Multiple proprietary protocols */
 #define ETH_P_AOE	0x88A2		/* ATA over Ethernet		*/
+#define ETH_P_ETHERCAT	0x88A4		/* EtherCAT			*/
 #define ETH_P_8021AD	0x88A8          /* 802.1ad Service VLAN		*/
 #define ETH_P_802_EX1	0x88B5		/* 802.1 Local Experimental 1.  */
 #define ETH_P_PREAUTH	0x88C7		/* 802.11 Preauthentication */