UBIFS: use nicer 64-bit math

Instead of using do_div(), use better primitives from
linux/math64.h.

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

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

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

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

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

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

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