[PATCH v2 REBASED] mtd: nand: pxa3xx-nand: prevent DFI bus lockup on removal

[Brian Norris]

On Mon, Sep 28, 2015 at 10:56:51PM +0200, Robert Jarzmik wrote:
> After the conversion of pxa architecture to common clock framework, the
> NAND clock can be disabled on driver exit.
> 
> In this case, it happens that if the driver used the NAND and set the
> DFI arbitration bit, the next access to a static memory controller area,
> such as an ethernet card, will stall the system bus, and the core will
> be stalled forever.
> 
> This is especially true on pxa31x SoCs, where the NDCR was augmented
> with a new bit to prevent this lockups by giving full ownership of the
> DFI arbiter to the SMC, in change SCr#6.
> 
> Fix this by clearing the DFI arbritration bit in driver exit. This
> effectively prevents a lockup on zylonite when removing pxa3xx-nand
> module, and using ethernet afterwards.
> 
> Signed-off-by: Robert Jarzmik <robert.jarzmik at free.fr>
> 
> ---
> Since v1: add comment, switch to NFCV1/NCFV2 registers naming
> Since v2: rebase on top of Brian's tree

Applied to l2-mtd.git. Thanks.