91zipl tries to read the filesystem for the /boot/zipl device.
On SLE12, however, the ext2 and ext3 filesystems are handled
by the ext4 module.
And due to bug#886839 no error is registered and booting fails.
So implement a band-aid to translate it into ext4.
Signed-off-by: Hannes Reinecke <hare@suse.de>