usb: usbip: vudc: Rename find_endpoint() to vudc_find_endpoint()

As find_endpoint() is a global funcion rename it to vudc_find_endpoint()
to clearly mark where does it come from.

Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>