ssb: add dma_dev to ssb_device structure

Add dma_dev, a pointer to struct device, to struct ssb_device.  We pass it
to the generic DMA API with SSB_BUSTYPE_PCI and SSB_BUSTYPE_SSB.
ssb_devices_register() sets up it properly.

This is preparation for replacing the ssb bus specific DMA API (ssb_dma_*)
with the generic DMA API.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Michael Buesch <mb@bu3sch.de>
Cc: Gary Zambrano <zambrano@broadcom.com>
Cc: Stefano Brivio <stefano.brivio@polimi.it>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John W. Linville <linville@tuxdriver.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>