staging: ks7010: change ETHER_HDR_SIZE definition to use the size of struct ether_hdr

This commit changes ETHER_HDR_SIZE definition which is a hardcoded
number using the size of the structure ether_hdr which is the one
for what this definition has been created. This improves readability
and makes clear the intention of this definition along the code.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ks7010/eap_packet.h

@@ -6,8 +6,6 @@
 #include <linux/bitops.h>
 #include <uapi/linux/if_ether.h>
 
-#define ETHER_HDR_SIZE 20
-
 struct ether_hdr {
 	unsigned char h_dest[ETH_ALEN];	/* destination eth addr */
 	unsigned char h_source[ETH_ALEN];	/* source ether addr    */
@@ -19,6 +17,8 @@ struct ether_hdr {
 	/* followed by length octets of data */
 } __packed;
 
+#define ETHER_HDR_SIZE sizeof(struct ether_hdr)
+
 struct ieee802_1x_hdr {
 	unsigned char version;
 	unsigned char type;