video, sm501: add I/O functions for use on powerpc

- add read/write functions for using this driver
  also on powerpc plattforms

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: linux-fbdev@vger.kernel.org
cc: devicetree-discuss@ozlabs.org
cc: Ben Dooks <ben@simtec.co.uk>
cc: Vincent Sanders <vince@simtec.co.uk>
cc: Samuel Ortiz <sameo@linux.intel.com>
cc: linux-kernel@vger.kernel.org
cc: Randy Dunlap <rdunlap@xenotime.net>
cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>