backlight: Add OMAP1 PWL backlight driver

This adds the OMAP1 PWL-based LCD backlight driver.  It's been in the OMAP
tree for some time.  Note that OMAP2 can do similar things with the generic
timers which have PWM outputs.  Such timers are more generic than the PWL
found on OMAP1 chips, but have a different EMI profile because they aren't
driven by a pseudorandom number generator.

[akpm@linux-foundation.org: cleanups]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrzej Zaborowski <balrogg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>