sata_dwc_460ex: move to generic DMA driver

The SATA implementation based on two actually different devices, i.e. SATA and
DMA controllers.

For Synopsys DesignWare DMA we have already a generic implementation of the
driver. Thus, the patch converts the code to use DMAEngine framework and
dw_dmac driver.

In future it will be better to split the devices inside DTS as well like it's
done on other platforms.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>