Fix compile failure if BACKLIGHT_CLASS_DEVICE is not selected

[Ian Molton]

>From 48c709c621dbd5505b524e0216a3232ebd0033a8 Mon Sep 17 00:00:00 2001
From: Ian Molton <imolton at ad-holdings.co.uk>
Date: Tue, 13 Jan 2015 12:46:54 +0000
Subject: [PATCH] DRM: Simple panel driver depends on backlight

The DRM_PANEL_SIMPLE option compiles code that requires the symbol
of_find_backlight_by_node. This is in drivers/video/backlight/backlight.c
and can optionally not be built. Make DRM_PANEL_SIMPLE depend on
BACKLIGHT_CLASS_DEVICE to resolve this.

drivers/built-in.o: In function `panel_simple_platform_probe':
debugfs.c:(.text+0x94da4): undefined reference to `of_find_backlight_by_node'
/home/ian/Work/swan/linux/Makefile:923: recipe for target 'vmlinux' failed


Signed-off-by: Ian Molton <imolton at ad-holdings.co.uk>
---
 drivers/gpu/drm/panel/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index bee9f72..d718acf 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -9,7 +9,7 @@ menu "Display Panels"

 config DRM_PANEL_SIMPLE
        tristate "support for simple panels"
-       depends on OF
+       depends on OF && BACKLIGHT_CLASS_DEVICE
        help
          DRM panel driver for dumb panels that need at most a regulator and
          a GPIO to be powered up. Optionally a backlight can be attached so
-- 
2.1.0