Instead of naming all ubi devices and cdev names ubi<num> append
'.ubi' to the original mtd name. This makes ubi device and cdev
names predictable. With this ubi0 becomes nand0.root.ubi. Also
do the same for volume names, so ubi0.root becomes nand0.root.ubi.root.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>