bbb-nand-sync: fix: use fdisk over parted

Assertion (head_size <= 63) at ../../../libparted/labels/dos.c:662 in function probe_partition_for_geom() failed.

./beaglebone-black-sync-nand.sh: line 50:  2491 Aborted                 parted --script ${DISK} set 1 boot on

Reported-by: Stephen Koone <skoone@gmail.com>
Signed-off-by: Robert Nelson <robertcnelson@gmail.com>