net,marvell: Add dependency on HAS_IOMEM

On archs like S390 or um this driver cannot build nor work.
Make it depend on HAS_IOMEM to bypass build failures.

drivers/built-in.o: In function `orion_mdio_probe':
drivers/net/ethernet/marvell/mvmdio.c:228: undefined reference to `devm_ioremap'

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/marvell/Kconfig b/drivers/net/ethernet/marvell/Kconfig
index a49e81b..6300fd2 100644
--- a/drivers/net/ethernet/marvell/Kconfig
+++ b/drivers/net/ethernet/marvell/Kconfig
@@ -33,6 +33,7 @@
 
 config MVMDIO
 	tristate "Marvell MDIO interface support"
+	depends on HAS_IOMEM
 	select PHYLIB
 	---help---
 	  This driver supports the MDIO interface found in the network