net: dhcp6: pxe: Add DHCP/PXE commands for IPv6

Adds commands to support DHCP and PXE with IPv6.

New configs added:
- CMD_DHCP6
- DHCP6_PXE_CLIENTARCH
- DHCP6_PXE_DHCP_OPTION
- DHCP6_ENTERPRISE_ID

New commands added (when IPv6 is enabled):
- dhcp6
- pxe get -ipv6
- pxe boot -ipv6

Signed-off-by: Sean Edmond <seanedmond@microsoft.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>

cmd/sysboot.c

@@ -101,7 +101,7 @@ static int do_sysboot(struct cmd_tbl *cmdtp, int flag, int argc,
 	}
 
 	if (pxe_setup_ctx(&ctx, cmdtp, sysboot_read_file, &info, true,
-			  filename)) {
+			  filename, false)) {
 		printf("Out of memory\n");
 		return CMD_RET_FAILURE;
 	}