usb: gadget: uvc: Configure the streaming endpoint based on the speed

Call the appropriate usb_ep_autoconf*() function depending on the device
speed, and pass it the corresponding streaming endpoint.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>