m68k/nommu: stop using GENERIC_IOMAP

m68k/nommu: stop using GENERIC_IOMAP

There is no need to go through the GENERIC_IOMAP wrapper for PIO on
nommu platforms, since these always come from PCI I/O space that is
itself memory mapped.

Instead, the generic ioport_map() can just return the MMIO location
of the ports directly by applying the PCI_IO_PA offset, while
ioread32/iowrite32 trivially turn into readl/writel as they do
on most other architectures.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>