[fallback] Avoid duplicate old BootOrder

set_boot_order() already copies the old BootOrder to the variable,
bootorder. Besides, we can adjust BootOrder when adding the newly
generated boot option. So, we don't have to copy the old one again
in update_boot_order(). This avoid the duplicate entries in BootOrder.

Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
[fallback] Fix the data size for boot option comparison

Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
[fallback] Try to boot the first boot option anyway

Some UEFI implementations never care the boot options, so the
restored boot options could be just ignored and this results in
endless reboot. To avoid this situation, this commit makes
fallback.efi to load the first matched boot option even if there
is no boot option to be restored. It may not be perfect, but at
least the bootloader is loaded...

Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>