initscripts: populate-volatile.sh: do not log to tty0

tty0 may not be the intended console for log messages, or it may not
exist at all in kernel configurations without CONFIG_VT. Just use the
default stdout/stderr instead.

Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>