Add a simple test of booting with the EFI bootmeth, which runs the app
and checks that it can call 'exit boot-services' (to check that all the
device-removal code doesn't break anything) and then exit back to
U-Boot.
This uses a disk image containing the testapp, ready for execution by
sandbox when needed.
Signed-off-by: Simon Glass <sjg@chromium.org>
70b78d5293