usb: gadget: uvc: Use strlcpy instead of strncpy

For NULL terminated string, better notice '\0' in the end.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
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>