linux-phytec-ti

ata: select DW_DMAC in case of SATA_DWC

Since sata_dwc_460ex.c was moved to generic DMA driver we have to ensure that
user can still compile it.

Fixes: 8b3444852a2b (sata_dwc_460ex: move to generic DMA driver)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>