rootfs.py: change the notice about deferring scripts to first boot from warning to a note
Now that the first boot deferral needs to be requested explicitly,
it's not really something to be concerned about.
Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>