usb: dwc3: keystone: Add support for ti,am654-dwc3

The AM654 SoC contains a DWC3 controller with TI specific
wrapper. Add support for that.

Unlike the Keystone 2 case, for AM654 We don't need to
process any IRQs for basic USB operation.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>