CHROMIUM: leds: Add Chrome OS keyboard LEDs driver

It is ACPI-based keyboard backlight LEDs.

BUG=chromium-os:32959
TEST=None (see next patch(es) for build/test info)

Change-Id: I0871851b1c67af33a9b9bd83c1dc93b1f8253ac5
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/31541
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

Conflicts:
	drivers/leds/Makefile
leds: chromeos keyboard name should contain "kbd_backlight"

The driver sysfs directory should be "chromeos::kbd_backlight"
This is to match how other keyboard backlight drivers do it.

BUG=chromium-os:32959
TEST=See /sys/class/leds, there should be "chromeos::kbd_backlight"

Change-Id: Icaed85f110211a1e51f15ebcbb90b9e9b5e63291
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/31626
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
CHROMIUM: leds: Fix chromeos keyboard LED suspend behavior

Should use the built-in suspend/resume functions in led-class.c instead.

Also renamed the set function to correctly reflect the device type.

BUG=chrome-os-partner:13273
TEST=set the keyboard backlight to various levels (low, medium, full)
and run powerd_suspend.  The backlight should turn off.  Resume.  The
backlight should be restored to its previous value (maybe with a delay).

Change-Id: Ifd56debd6f157b71729bf563b4242c58709549f7
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/31722
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>