drivers/net/phy/Kconfig: Let MDIO_BCM_UNIMAC depend on HAS_IOMEM

MDIO_BCM_UNIMAC needs HAS_IOMEM, so depend on it, the related error (
with allmodconfig under um):

    MODPOST 1205 modules
  ERROR: "devm_ioremap" [drivers/net/phy/mdio-bcm-unimac.ko] undefined!
Signed-off-by: NChen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -205,6 +205,7 @@ config MDIO_BUS_MUX_MMIOREG
 
 config MDIO_BCM_UNIMAC
 	tristate "Broadcom UniMAC MDIO bus controller"
+	depends on HAS_IOMEM
 	help
 	  This module provides a driver for the Broadcom UniMAC MDIO busses.
 	  This hardware can be found in the Broadcom GENET Ethernet MAC