x86: Add support for U-Boot as an EFI application

Add the required x86 glue code. This includes the initial start-up,
relocation and jumping to efi_main(). We also need to avoid fiddling with
interrupts.

Signed-off-by: Ben Stoltz <stoltz@google.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 36a6018..d104a49 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -2,7 +2,9 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
+ifeq ($(CONFIG_EFI_APP),)
 head-y := arch/x86/cpu/start.o
+endif
 ifeq ($(CONFIG_SPL_BUILD),y)
 head-y += arch/x86/cpu/start16.o
 head-y += arch/x86/cpu/resetvec.o