x86: Add EFI board code

Add support for the efi-x86 board, which supports running U-Boot as an
EFI 32-bit application.

Signed-off-by: Ben Stoltz <stoltz@google.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7e6e89c..f124d58 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -27,6 +27,7 @@
 
 # board-specific options below
 source "board/coreboot/Kconfig"
+source "board/efi/Kconfig"
 source "board/emulation/Kconfig"
 source "board/google/Kconfig"
 source "board/intel/Kconfig"