usb: driver: nordic: Unlock mutex in case of error.
usb: driver: nordic: Unlock mutex in case of error.

Mutex that was previously locked must be unlocked in case
of an error.

Signed-off-by: Emil Obalski <a38006c9a9911dcd7c7e26537de6a2fa1043ca9e@nordicsemi.no>

finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr