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>
