HID: hid-lg4ff: Export the real wheel model and supported alternate modes

Display the real wheel model and supported alternate modes through sysfs. This
applies only to multimode wheels.
Signed-off-by: Michal Malý <madcatxster@devoid-pointer.net>
Tested-by: Simon Wood <simon@mungewell.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/ABI/testing/sysfs-driver-hid-logitech-lg4ff

@@ -5,3 +5,23 @@ Contact:	Michal Malý <madcatxster@gmail.com>
 Description:	Display minimum, maximum and current range of the steering
 		wheel. Writing a value within min and max boundaries sets the
 		range of the wheel.
+
+What:		/sys/bus/hid/drivers/logitech/<dev>/alternate_modes
+Date:		Feb 2015
+KernelVersion:	4.1
+Contact:	Michal Malý <madcatxster@gmail.com>
+Description:	Displays a set of alternate modes supported by a wheel. Each
+		mode is listed as follows:
+		  Tag: Mode Name
+		Currently active mode is marked with an asterisk. List also
+		contains an abstract item "native" which always denotes the
+		native mode of the wheel.
+
+What:		/sys/bus/hid/drivers/logitech/<dev>/real_id
+Date:		Feb 2015
+KernelVersion:	4.1
+Contact:	Michal Malý <madcatxster@gmail.com>
+Description:	Displays the real model of the wheel regardless of any
+		alternate mode the wheel might be switched to.
+		It is a read-only value.
+		This entry is not created for devices that have only one mode.