initrdpack: use /var/lib/elbe instead of /var/cache/elbe

Signed-off-by: Manuel Traut <manut@linutronix.de>
elbe-bootstrap: update path of files

elbe-bootstrap_1.0 was updated to use /var/lib/elbe instead of /opt/elbe
to store the ramdisk and kernel.

Signed-off-by: Manuel Traut <manut@linutronix.de>