ubifs: Remove redundant assignment ...

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: cleanup backingstore handling ...

All filesystem drivers which need a backingstore device do the same
ignoring of '/dev/' in the backingstore followed by a cdev_open. Add a
helper function for it and let the core handle the cdev. As a side
effect this makes sure that fsdev->cdev is also set when a device is
mounted without the leading '/dev/' which was previously ignored
by the mount code.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: Add ubifs support ...

This adds ubifs support from u-boot-2013.07. This is taken
mostly as-is, only the necessary adjustments to attach to the
barebox fs layer have been made.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>