UBIFS: fix writing uncompressed files

UBIFS does not disable compression if ui->flags is non-zero, e.g.
if the file has "sync" flag. This is because of the typo which
is fixed by this patch. The patch also adds a couple of useful
debugging prints.

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