usb: gadget: printer: eliminate file global printer_mutex
usb: gadget: printer: eliminate file global printer_mutex

The mutex is a legacy after semi-automatic Big Kernel Lock removal.
printer_open() does its own locking, so no need to duplicate it.

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