efi: Create a 64-bit app

Most modern platforms use 64-bit EFI so it is useful to have a U-Boot app
that runs under that. Add a (non-functional) build for this.

Note that --whole-archive causes the gcc 9.2 linker to crash, so disable
this for now. Once this is resolved, things should work.

For now, avoid mentioning the documentation for the 64-bit app, since it
does not work.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index fa7fe90..00ff572 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -709,6 +709,9 @@
 M:	Heinrich Schuchardt <xypron.glpk@gmx.de>
 S:	Maintained
 W:	https://u-boot.readthedocs.io/en/latest/develop/uefi/u-boot_on_efi.html
+F:	board/efi/efi-x86_app
+F:	configs/efi-x86_app*
+F:	doc/develop/uefi/u-boot_on_efi.rst
 F:	lib/efi/efi_app.c
 F:	scripts/build-efi.sh