sh: fix build error by adding generic ioport_{map/unmap}()

Fix build error as reported by Geert Uytterhoeven here:

  http://kisskb.ellerman.id.au/kisskb/buildresult/11607865/

The error happens when CONFIG_HAS_IOPORT_MAP=n because of which there
are missing definitions of ioport_map/unmap().  Fix this build error by
adding these prototypes.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: <stable@vger.kernel.org>	[3.16+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>