drm/omap: ensure we have a valid dma_mask

The omapdrm driver uses dma_set_coherent_mask(), but that's not enough
anymore when LPAE is enabled.

From Christoph Hellwig <[e-mail]>:

> The traditional arm DMA code ignores, but the generic dma-direct/swiotlb
> has stricter checks and thus fails mappings without a DMA mask. As we
> use swiotlb for arm with LPAE now, omapdrm needs to catch up and
> actually set a DMA mask.

Change the dma_set_coherent_mask() call to
dma_coerce_mask_and_coherent() so that the dev->dma_mask is also set.

Fixes: ad3c7b18c5b3 ("arm: use swiotlb for bounce buffering on LPAE configs")
Reported-by: "H. Nikolaus Schaller" <[e-mail]>
Signed-off-by: Tomi Valkeinen <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Peter Ujfalusi <[e-mail]>

drivers/gpu/drm/omapdrm/omap_drv.c

···
 	if (omapdss_is_initialized() == false)
 		return -EPROBE_DEFER;
 
-	ret = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
+	ret = dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to set the DMA mask\n");
 		return ret;