UBIFS: change bud replay function conventions

This is a minor preparation patch which changes 'replay_bud()' interface -
instead of passing bud lnum, offs, jhead, etc directly, pass a pointer to the
bud entry which contains all the information. The bud entry will be also needed
in one of the following patches.

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