efi_loader: optional persistence of variables

Since be66b89da306 ("efi_loader: configuration of variables store")
the choice of EFI_VARIABLE_FILE_STORE or EFI_MM_COMM_TEE
is mutually-exclusive, however efi_var_to_file also allows
for "neither". Provide an additional Kconfig option.

Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 28657f5..759cd2a 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -62,11 +62,18 @@
 	  variable related operations to that. The application will verify,
 	  authenticate and store the variables on an RPMB.
 
+config EFI_VARIABLE_NO_STORE
+	bool "Don't persist non-volatile UEFI variables"
+	help
+	  If you choose this option, non-volatile variables cannot be persisted.
+	  You could still provide non-volatile variables via
+	  EFI_VARIABLES_PRESEED.
+
 endchoice
 
 config EFI_VARIABLES_PRESEED
 	bool "Initial values for UEFI variables"
-	depends on EFI_VARIABLE_FILE_STORE
+	depends on !EFI_MM_COMM_TEE
 	help
 	  Include a file with the initial values for non-volatile UEFI variables
 	  into the U-Boot binary. If this configuration option is set, changes