rauc-mark-good: Backup the boot partition
rauc-mark-good: Backup the boot partition

Before marking the partition as good, backup the current partition
to the other partition in case of rediscovery so each boot partition
will successfully use the overlay.

Signed-off-by: Bill Pittman <43ac99c9c99efa205ddaaebf4c7bd970d58e135c@ni.com>
Acked-by: Haris Okanovic <4f2c24956fa4a8756878315db434b9fed29fa615@ni.com>
Natinst-ReviewBoard-ID: 310630

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt