net: wiznet add missing HAS_IOMEM dependency

The "WIZnet devices" config option should depend on HAS_IOMEM as
all wiznet drivers require it as well.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>