CAN: softing driver depends on IOMEM

Without this dependency the softing driver will be buildable on s390,
where it fails.
Signed-Off-By: Chuck Ebbert <cebbert@redhat.com>
Acked-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/can/softing/Kconfig

 config CAN_SOFTING
 	tristate "Softing Gmbh CAN generic support"
-	depends on CAN_DEV
+	depends on CAN_DEV && HAS_IOMEM
 	---help---
 	  Support for CAN cards from Softing Gmbh & some cards
 	  from Vector Gmbh.