Driver was checking for direct mode but not locking it.  Use
claim/release helper functions to guarantee the device stays
in direct mode during all raw write operations.
Signed-off-by: NAlison Schofield <amsfield22@gmail.com>
Acked-by: NPeter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>