efi_loader: Add network access support

We can now successfully boot EFI applications from disk, but users
may want to also run them from a PXE setup.

This patch implements rudimentary network support, allowing a payload
to send and receive network packets.

With this patch, I was able to successfully run grub2 with network
access inside of QEMU's -M xlnx-ep108.

Signed-off-by: Alexander Graf <agraf@suse.de>

net/bootp.c

@@ -10,6 +10,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <efi_loader.h>
 #include <net.h>
 #include <net/tftp.h>
 #include "bootp.h"
@@ -1025,6 +1026,7 @@ static void dhcp_handler(uchar *pkt, unsigned dest, struct in_addr sip,
 			    strlen(CONFIG_SYS_BOOTFILE_PREFIX)) == 0) {
 #endif	/* CONFIG_SYS_BOOTFILE_PREFIX */
 			dhcp_packet_process_options(bp);
+			efi_net_set_dhcp_ack(pkt, len);
 
 			debug("TRANSITIONING TO REQUESTING STATE\n");
 			dhcp_state = REQUESTING;