UBIFS: increment commit number earlier

Increment the commit number at the beginnig of the commit, instead
of doing this after the commit. This is needed for further
optimizations.

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

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

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

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

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