usb: gadget: printer: remove unused and empty printer_unbind
usb: gadget: printer: remove unused and empty printer_unbind

The unbind() method is optional is usb_composite_driver.
In this particular driver the method does nothing so it can be removed.

Signed-off-by: Andrzej Pietrasiewicz <0bcd4dade8bc9135441847460b651a5ef589ec79@samsung.com>
Signed-off-by: Felipe Balbi <94dddeeef08b001e003cce128ddc162a4e2c6cd2@ti.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs