efi_loader: using EFI_UNSUPPORTED for private authenticated variables

Improve error message for UEFI SCT tests.

Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
1 file changed