usb: musb: dma: Add a DMA completion platform callback

Currently, the CPPI 4.1 driver is not completely generic and
only works on DSPS. This is because of IRQ management.
Add a callback to dma_controller that could be invoked on DMA completion
to acknowledge the IRQ.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>