Rootfs overlays get created at a ROOTDEV_OVERLAY_ALIGN (64KiB)
alignment after the rootfs, but emmc_do_upgrade() is assuming
it comes at the very next 512-byte sector.
Suggested-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
(move spaces around, mention fstools' libtoolfs)
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>