sh: machvec IO death.

This takes a bit of a sledgehammer to the machvec I/O routines. The
iomem case requires no special casing and so can just be dropped
outright. This only leaves the ioport casing for PCI and SuperIO
mangling. With the SuperIO case going through the standard ioport
mapping, it's possible to replace everything with generic routines.

With this done the standard I/O routines are tidied up and NO_IOPORT
now gets default-enabled for the vast majority of boards.

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