sh: pci io port base address code

Adds a __get_pci_io_base() function which is used to match a port range
against struct pci_channel. This allows us to detect if a port range is
assigned to pci or happens to be legacy port io. While at it, remove unused
cpu-specific cruft.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>