sh: sh7751 pci controller io port fix

This patch updates the sh7751 pci code to handle io ports
correctly. The code is based on the sh7788x implementation.

Tested on a R2D-1 board with CONFIG_8139TOO_PIO=y.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>