pci: sh7751: fix up PCI I/O space address

pci: sh7751: fix up PCI I/O space address

The change actually maps PCI I/O window to the same address on PCI bus
as it is stated by a comment, before the change transfers to the PCI I/O
space are failed due to misconfiguration of the most significant 14 bits
of the PCI address in PCIIOBR (note that it is set to 0x0).

Most probably the problem remained unnoticed, because communcation
to all tested PCI devices is done over PCI memory space only.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>