net: cs89x0: always build platform code if !HAS_IOPORT_MAP

The cs89x0 driver can either be built as an ISA driver or a platform
driver, the choice is controlled by the CS89x0_PLATFORM Kconfig
symbol. Building the ISA driver on a system that does not have
a way to map I/O ports fails with this error:

drivers/built-in.o: In function `cs89x0_ioport_probe.constprop.1':
:(.init.text+0x4794): undefined reference to `ioport_map'
:(.init.text+0x4830): undefined reference to `ioport_unmap'

This changes the Kconfig logic to take that option away and
always force building the platform variant of this driver if
CONFIG_HAS_IOPORT_MAP is not set. This is the only correct
choice in this case, and it avoids the build error.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>