Revert "Documentation: Add entry for dell-laptop sysfs interface"

This reverts commit 3161293b.

This interface was determined to be flawed and required too invasive a
fix for the RC cycle. This will be revisited in 3.20.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

Documentation/ABI/testing/sysfs-platform-dell-laptop

-What:		/sys/class/leds/dell::kbd_backlight/als_setting
-Date:		December 2014
-KernelVersion:	3.19
-Contact:	Gabriele Mazzotta <gabriele.mzt@gmail.com>,
-		Pali Rohár <pali.rohar@gmail.com>
-Description:
-		This file allows to control the automatic keyboard
-		illumination mode on some systems that have an ambient
-		light sensor. Write 1 to this file to enable the auto
-		mode, 0 to disable it.
-
-What:		/sys/class/leds/dell::kbd_backlight/start_triggers
-Date:		December 2014
-KernelVersion:	3.19
-Contact:	Gabriele Mazzotta <gabriele.mzt@gmail.com>,
-		Pali Rohár <pali.rohar@gmail.com>
-Description:
-		This file allows to control the input triggers that
-		turn on the keyboard backlight illumination that is
-		disabled because of inactivity.
-		Read the file to see the triggers available. The ones
-		enabled are preceded by '+', those disabled by '-'.
-
-		To enable a trigger, write its name preceded by '+' to
-		this file. To disable a trigger, write its name preceded
-		by '-' instead.
-
-		For example, to enable the keyboard as trigger run:
-		    echo +keyboard > /sys/class/leds/dell::kbd_backlight/start_triggers
-		To disable it:
-		    echo -keyboard > /sys/class/leds/dell::kbd_backlight/start_triggers
-
-		Note that not all the available triggers can be configured.
-
-What:		/sys/class/leds/dell::kbd_backlight/stop_timeout
-Date:		December 2014
-KernelVersion:	3.19
-Contact:	Gabriele Mazzotta <gabriele.mzt@gmail.com>,
-		Pali Rohár <pali.rohar@gmail.com>
-Description:
-		This file allows to specify the interval after which the
-		keyboard illumination is disabled because of inactivity.
-		The timeouts are expressed in seconds, minutes, hours and
-		days, for which the symbols are 's', 'm', 'h' and 'd'
-		respectively.
-
-		To configure the timeout, write to this file a value along
-		with any the above units. If no unit is specified, the value
-		is assumed to be expressed in seconds.
-
-		For example, to set the timeout to 10 minutes run:
-		    echo 10m > /sys/class/leds/dell::kbd_backlight/stop_timeout
-
-		Note that when this file is read, the returned value might be
-		expressed in a different unit than the one used when the timeout
-		was set.
-
-		Also note that only some timeouts are supported and that
-		some systems might fall back to a specific timeout in case
-		an invalid timeout is written to this file.