sh: Improved multi-resource handling for SH7780 PCI.

The SH7780 PCI controller supports 3 different ranges of PCI memory in
addition to its PCI I/O window. In the case of 29-bit mode, only 2 memory
windows are supported, while in 32-bit mode all 3 are visible. This
attempts to make the resource handling completely dynamic and to permit
platforms to map in as many apertures as they can handle.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>