efi_loader: fix BootOrder variable measurement handling

UEFI specification does not require that BootOrder is defined.
In current implementation, boot variable measurement fails and
returns EFI_NOT_FOUND if BootOrder is not defined.

This commit correcly handles this case, skip the boot variable
measurement if BootOrder is not defined.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 586f73a..189e4a5 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -1452,8 +1452,8 @@
 	boot_order = efi_get_var(var_name, &efi_global_variable_guid,
 				 &var_data_size);
 	if (!boot_order) {
-		ret = EFI_NOT_FOUND;
-		goto error;
+		/* If "BootOrder" is not defined, skip the boot variable measurement */
+		return EFI_SUCCESS;
 	}
 
 	ret = tcg2_measure_variable(dev, 1, EV_EFI_VARIABLE_BOOT2, var_name,