fbdev: LCD backlight driver using Atmel PWM driver

This patch adds a platform driver using the ATMEL PWM driver to control a
backlight which requires a PWM signal and optional GPIO signal for discrete
on/off signal.  It has been tested on Favr-32 board from EarthLCD.

The driver is configurable by supplying a struct with the platform data.  See
the include/linux/atmel-pwm-bl.h for details.

The board code for Favr-32 will be submitted to the AVR32 kernel list.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>