ideapad: add backlight driver
ideapad: add backlight driver

When acpi_backlight=vendor in cmdline or no backlight support in acpi video
device, ideapad-laptop will register backlight device and control brightness
and backlight power via the command in VPC2004.

Signed-off-by: Ike Panhc <42a4cc10d9fafa45ebd4109d2131c3f152800229@canonical.com>
Signed-off-by: Matthew Garrett <4cf8d479716eba9bc68e0146d95320fcb138b96b@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs