sh: pci: Rework SH7780 host controller detection.

This reworks how the host controller is probed, and makes it a bit more
verbose in the event a new type of controller is detected. Additionally,
we also log the revision information.

This now uses the proper access sizes for the vendor/device registers,
rather than relying on a larger access that encapsulated both of them.
Not all devices support 32-bit read cycles for these registers.

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