This is already dealt with in the new build scripts so that we use the UUID and don't hardcode a device. I'm not sure why you're not finding the device, as there should only be 1 partition on the banana-pro image, however, if you'd like to fix this up for yourself and have another linux machine (or virtual machine you can plug the sdcard into)...

run

sudo blkid -s UUID -o value /dev/sda1 (or whatever the partition is when you plug the sdcard into your other machine/virtualmachine)

You can edit the /boot/extlinux/extlinux.conf file to change the root= line from "root=/dev/mmcblk0p1" to "root=UUID=$VALUEOFTHECOMMANDABOVE" (without the $)

You might want to also check the /etc/default/u-boot file and make sure it doesn't have it hardcoded there, so that it doesn't revert the change (and make the same change as above to it!)