efi_loader: UEFI variable persistence

Persist non-volatile UEFI variables in a file on the EFI system partition.

The file is written whenever a non-volatile UEFI variable is changed after
initialization of the UEFI sub-system.

The file is read during the UEFI sub-system initialization to restore
non-volatile UEFI variables.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index 7eddd7e..c87b82d 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -40,6 +40,7 @@
 obj-y += efi_variable_tee.o
 else
 obj-y += efi_variable.o
+obj-y += efi_var_file.o
 endif
 obj-y += efi_watchdog.o
 obj-$(CONFIG_LCD) += efi_gop.o