Merge branch 'linux-next' of git://git.infradead.org/ubi-2.6
* 'linux-next' of git://git.infradead.org/ubi-2.6:
UBI: clarify the volume notification types' doc
UBI: remove dead code
UBI: dump stack when switching to R/O mode
UBI: fix oops in error path
UBI: switch debugging tests knobs to debugfs
UBI: make it possible to use struct ubi_device in debug.h
UBI: prepare debugging stuff to further debugfs conversion
UBI: use debugfs for the extra checks knobs
UBI: change the interface of a debugging check function