usb: dwc2: gadget: Adjust ISOC OUT request's actual len for DDMA

In DDMA mode if programmed ISOC OUT transfer length is not DWORD
aligned, after closing descriptor HW leaves value of 4 - (ureq->length %
4) in the RX bytes. This is caused because DMA works using 4B chunks.
Example: if length = 9 and all 9 bytes were received from the bus, after
xfercomplete rx_bytes value is 3. Hence add this value to the amount of
transferred bytes.

Signed-off-by: Vahram Aharonyan <vahrama@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>