Update now that if_ether.h has moved.

src/core/vsprintf.c

 #include <stdarg.h>
-#include "if_ether.h" /* for ETH_ALEN */
+#include <gpxe/if_ether.h> /* for ETH_ALEN */
 #include "limits.h" /* for CHAR_BIT */
 #include "console.h"
 #include "errno.h"

src/include/gpxe/in.h

 #ifndef	_IN_H
 #define	_IN_H
 
-#include "stdint.h"
-#include <if_ether.h>
-#define IP		ETH_P_IP
-#define ARP		ETH_P_ARP
-#define	RARP		ETH_P_RARP
+#include <stdint.h>
 
 #define IP_ICMP		1
 #define IP_IGMP		2