can: softing: remove redundant NULL check

In this case dev cannot be NULL, so remove redundant check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 03fd3cf ("can: add driver for Softing card")
Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
Link: https://lore.kernel.org/all/20240211150535.3529-1-d.dulov@aladdin.ru
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/softing/softing_fw.c

@@ -436,7 +436,7 @@ int softing_startstop(struct net_device *dev, int up)
 		return ret;
 
 	bus_bitmask_start = 0;
-	if (dev && up)
+	if (up)
 		/* prepare to start this bus as well */
 		bus_bitmask_start |= (1 << priv->index);
 	/* bring netdevs down */