can: esd_usb2: fix memory leak on disconnect

commit efbd50d2f62fc1f69a3dcd153e63ba28cc8eb27f upstream.

It seems struct esd_usb2 dev is not deallocated on disconnect. The patch adds
the missing deallocation.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>