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