UBI: fix kernel-doc errors and warnings

No functional changes, just tweak comments to make kernel-doc
work fine and stop complaining.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

diff --cc drivers/mtd/ubi/build.c
Simple merge

diff --cc drivers/mtd/ubi/io.c
Simple merge

diff --cc drivers/mtd/ubi/scan.c
Simple merge

diff --cc drivers/mtd/ubi/ubi.h
Simple merge

diff --cc drivers/mtd/ubi/upd.c
Simple merge

diff --cc drivers/mtd/ubi/vmt.c
Simple merge

diff --cc drivers/mtd/ubi/vtbl.c
Simple merge

diff --cc drivers/mtd/ubi/wl.c
Simple merge