sh: Reworked SH7780 PCI initialization.

This consolidates the PCI initialization code for all of the pci-sh7780
users, and sets up the memory window dynamically as opposed to using
hardcoded window positions.

A number of bugs were fixed at the same time, including the PIO handling
and master abort timeout settings being incorrect.

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