efi_loader: output load options in helloworld

We need to test if we pass a valid image handle when loading
and EFI application. This cannot be done in efi_selftest as
it is not loaded as an image.

So let's enhance helloworld a bit.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>