Correct some compile erros.

grub-core/Makefile.core.def

@@ -1503,7 +1503,7 @@ module = {
 module = {
   name = emunet;
   emu = net/drivers/emu/emunet.c;
-  enable = ieee1275;
+  enable = emu;
 };
 
 module = {

grub-core/kern/ieee1275/openfw.c

@@ -25,7 +25,6 @@
 #include <grub/ieee1275/ofnet.h>
 #include <grub/net/ieee1275/interface.h>
 #include <grub/net.h>
-#include <grub/net/disknet.h>
 #include <grub/net/tftp.h>
 
 grub_bootp_t (*grub_getbootp) (void);

grub-core/net/drivers/ieee1275/ofnet.c

@@ -1,4 +1,5 @@
 #include <grub/net/netbuff.h>
+#include <grub/net/ethernet.h>
 #include <grub/ieee1275/ofnet.h>
 #include <grub/ieee1275/ieee1275.h>
 #include <grub/dl.h>