usb: gadget: uvc: Fix endianness mismatches

The struct usb_endpoint_descriptor wMaxPacketSize field the struct
usb_ss_ep_comp_descriptor wBytesPerInterval field are stored in
little-endian format. Convert the values from CPU order to little endian
before storing the values.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>