Input: add driver for slidebar on Lenovo IdeaPad laptops

This driver adds support for slidebars found on some Lenovo IdeaPad
laptops (the slidebars work with SlideNav/Desktop Navigator under
Windows).

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=16004

Registers 'IdeaPad Slidebar' input device and
/sys/devices/platform/ideapad_slidebar/slidebar_mode
for switching slidebar's modes.

Now works on:
IdeaPad Y550, Y550P.

May work on (testing and adding new models is needed):
Ideapad Y560, Y460, Y450, Y650,
and, probably, some others.

Signed-off-by: Andrey Moiseev <o2g.org.ru@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/Makefile

@@ -61,3 +61,4 @@ obj-$(CONFIG_INPUT_WISTRON_BTNS)	+= wistron_btns.o
 obj-$(CONFIG_INPUT_WM831X_ON)		+= wm831x-on.o
 obj-$(CONFIG_INPUT_XEN_KBDDEV_FRONTEND)	+= xen-kbdfront.o
 obj-$(CONFIG_INPUT_YEALINK)		+= yealink.o
+obj-$(CONFIG_INPUT_IDEAPAD_SLIDEBAR)	+= ideapad_slidebar.o