of/platform: Initialise default DMA masks

When of_dma_configure() was first born in 591c1ee4 ("of: configure
the platform device dma parameters"), everything DMA-related was
factored out of of_platform_device_create_pdata() as seemed appropriate
at the time. However, now that of_dma_configure() has grown into the
generic handler for processing DMA-related properties from DT for all
kinds of devices, it is no longer an appropriate place to be doing
OF-platform-specific business. Since there are still plenty of platform
drivers not setting their own masks and depending on the bus default,
let's reinstate that inialisation in the OF-platform code itself, and
restore the long-standing status quo from 0589342c ("of: set
dma_mask to point to coherent_dma_mask")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/of/platform.c

@@ -185,6 +185,9 @@ static struct platform_device *of_platform_device_create_pdata(
 	if (!dev)
 		goto err_clear_flag;
 
+	dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
+	if (!dev->dev.dma_mask)
+		dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
 	dev->dev.bus = &platform_bus_type;
 	dev->dev.platform_data = platform_data;
 	of_msi_configure(&dev->dev, dev->dev.of_node);