UBIFS: add inode size debugging check

Add one more check to UBIFS - a check that makes sure that there
are no data nodes beyond inode size. And few commantaries fixes
along the line.

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

diff --cc fs/ubifs/debug.h
Simple merge

diff --cc fs/ubifs/key.h
Simple merge

diff --cc fs/ubifs/super.c
Simple merge

diff --cc fs/ubifs/tnc.c
Simple merge