Fix calculation of transfer size on completion in function
dwc2_gadget_get_xfersize_ddma().
Added increment of descriptor pointer to move to next descriptor in
the loop.
Fixes: aa3e8bc81311 ("usb: dwc2: gadget: DDMA transfer start and complete")
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>