can: j1939: fix memory leak if filters was set

Filters array is coped from user space and linked to the j1939 socket.
On socket release this memory was not freed.

Fixes: 9d71dd0c

 ("can: add support of SAE J1939 protocol")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>