usb: musb: dsps: Manage CPPI 4.1 DMA interrupt in DSPS

Despite the CPPI 4.1 is a generic DMA, it is tied to USB.
On the DSPS, CPPI 4.1 interrupt's registers are in USBSS (the MUSB glue).
Currently, to enable / disable and clear interrupts, the CPPI 4.1 driver
maps and accesses to USBSS's register, which making CPPI 4.1 driver not
really generic.
Move the interrupt management to DSPS driver.

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