backlight: Add driver for Tabletkiosk Sahara TouchIT-213 Tablet PC

[akpm@linux-foundation.org: coding-style fixes]
[rpurdie@linux.intel.com: minor tweaks]
Signed-off-by: Claudio Nieder <private@claudio.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>