UBIFS: fix assertions

I introduce wrong assertions in one of the previous commits, this
patch fixes them.

Also, initialize debugfs after the debugging check. This is a little
nicer because we want the FS data to be accessible to external users
after everything has been initialized.

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