CS89x0 : Use ioread16/iowrite16 on all platforms

The use of the inw/outw functions by the cs89x0 platform driver
results in NULL pointer references on ARM platforms and
platforms that do not provide ISA-style programmed I/O accessors.

Using inw/outw also accesses the wrong address space on platforms
that have a PCI I/O space that is not identity-mapped into the
physical address space.
Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>