usb: gadget: function: printer: Fix a memory leak for interface descriptor

usb: gadget: function: printer: Fix a memory leak for interface descriptor

When printer driver is loaded, the printer_func_bind function is called, in
this function, the interface descriptor be allocated memory, if after that,
the error occurred, the interface descriptor memory need to be free.

Reviewed-by: Peter Chen <peter.chen@nxp.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Link: https://lore.kernel.org/r/20201210020148.6691-1-qiang.zhang@windriver.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>