usb: dwc3: ep0: use _roundup_ to calculate the transfer size

No functional change. Used _roundup_ macro to calculate the transfer
size aligned to maxpacket in  dwc3_ep0_complete_data. It also makes it
similar to how transfer size is calculated in __dwc3_ep0_do_control_data.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>