bmlutils: Fix "Backup/Restore recovery on some devices"

Restoring recovery ($ flash_image recovery) will write recovery also on
the boot partition.
This behaviour should be disabled on some samsung phone in which boot
and recovery are different, in order to restore recovery without
overwrite boot.

It can be disabled via BOOT_AND_RECOVERY_ARE_DIFFERENT
Change-Id: Ie96a539806e8e8f0e4fc785b9be5ec02df9c3580