imx7: dev->coherent_dma_mask NULL warning

[Christoph Hellwig]

On Wed, Aug 18, 2021 at 06:31:19AM -0300, Fabio Estevam wrote:
> Correct, on i.MX7 the ath10k Wifi chip connects via SDIO.
> 
> Is there a way to avoid the WARN_ON_ONCE(!dev->coherent_dma_mask)
> to happen in this case?

The way to avoid it is by stoppind to use dma_alloc_attrs/coherent
on a device that is not DMA capable.