[U-Boot] efi_loader helloworld.efi: Fix building with -Os

[Alexander Graf]

> Depending on your compiler, when compiling the hello world efi binary
> with -Os, gcc might think it's a smart idea to replace common patterns
> such as memory copies with explicit calls to memcpy().
> 
> While that sounds great at first, we don't have any memcpy() available
> in our helloworld build target. So let's indicate to gcc that we really
> do want to have the code be built as freestanding.
> 
> Fixes: bbf75dd9 ("efi_loader: output load options in helloworld")
> Signed-off-by: Alexander Graf <agraf at suse.de>

Thanks, applied to efi-next

Alex