usb: dwc2: Update target (u)frame calculation

In service interval based scheduling target (u)frame must be
set as a last frame in this the service interval.

Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>