usb: gadget: printer: call gprinter_setup() from gadget's bind

Call gprinter_setup() from gadget's bind instead of module's init.
Call gprinter_cleaup() corerspondingly. This detaches printer function's
logic from legacy printer gadget's implementation.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>