ARM: multi_v7_defconfig: Enable BACKLIGHT_CLASS_DEVICE

Commit 72fee6b0 ("fbdev: Restrict FB_SH_MOBILE_LCDC to SuperH")
disabled availablity of the SH_MOBILE_LCDC driver on the RENESAS arch.
This innocent change has a significant side-effect on the ARM's
multi_v7_defconfig, because FB_BACKLIGHT symbol is no longer selected,
what in turn leaves BACKLIGHT_CLASS_DEVICE symbol selected only as
a module. The latter disables some backlight related code in the DRM
core, because the DRM core is set to be compiled-in in this defconfig.
This leaves all DRM display panels without integrated backlight control,
even if the needed modules have been properly loaded and probed.

Fix this by selecting BACKLIGHT_CLASS_DEVICE to be compiled-in in
multi_v7_defconfig.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/multi_v7_defconfig

@@ -777,6 +777,7 @@ CONFIG_FB_EFI=y
 CONFIG_FB_WM8505=y
 CONFIG_FB_SH_MOBILE_LCDC=y
 CONFIG_FB_SIMPLE=y
+CONFIG_BACKLIGHT_CLASS_DEVICE=y
 CONFIG_BACKLIGHT_PWM=y
 CONFIG_BACKLIGHT_AS3711=y
 CONFIG_BACKLIGHT_GPIO=y