sh: Provide stubbed I/O routines for NO_IOPORT case.

Too many drivers fail at IOPORT vs IOMEM checking before blindly calling
in to the API, so we may as well just provide basic stubs to get more
build coverage. Other platforms already do this, too (tile, parisc, etc.)

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