mcb: Add a dma_device to mcb_device

When performing DMA operations on a MCB device, the device needed
for using the DMA API is "mcb_device->bus_carrier".
This is rather lengthy, so a shortcut is introduced to struct mcb_device
in order to ensure the MCB device driver uses the correct device for DMA
operations.

Signed-off-by: Michael Moese <[e-mail]>
Signed-off-by: Johannes Thumshirn <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/mcb/mcb-core.c

···
 	dev->dev.bus = &mcb_bus_type;
 	dev->dev.parent = bus->dev.parent;
 	dev->dev.release = mcb_release_dev;
+	dev->dma_dev = bus->carrier;
 
 	device_id = dev->id;
 	dev_set_name(&dev->dev, "mcb%d-16z%03d-%d:%d:%d",

include/linux/mcb.h

···
 	int rev;
 	struct resource irq;
 	struct resource mem;
+	struct device *dma_dev;
 };
 
 static inline struct mcb_device *to_mcb_device(struct device *dev)