dma: cavs: Add gpdma derivative of dw dma for cavs

Intel's adsp needs to set, at a minimum, a clocking bit before the driver
can initialize the designware dma controller. In many ways it is the
designware dmac IP but with additional registers and functionality added
on top of it. So the code structure here follows how the hardware
appears to be designed, layered on top of the designware driver.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>