drm/gma500: remove unnecessary config_enabled() guard

Commit d112a816 ("gma500/cdv: Add eDP support") replaced the
code inside this if-conditional with gma_backlight_set(), which
becomes a nop stub if CONFIG_BACKLIGHT_CLASS_DEVICE is disabled.
So, there is no need to guard the caller with config_enabled().

Note:
This is one of remaining TODOs to deprecate config_enabled() macro.
Refer to commit 97f2645f ("tree-wide: replace config_enabled()
with IS_ENABLED()").
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1471970574-23906-1-git-send-email-yamada.masahiro@socionext.com

drivers/gpu/drm/gma500/opregion.c

@@ -163,10 +163,7 @@ static u32 asle_set_backlight(struct drm_device *dev, u32 bclp)
 	if (bclp > 255)
 		return ASLE_BACKLIGHT_FAILED;
 
-	if (config_enabled(CONFIG_BACKLIGHT_CLASS_DEVICE)) {
-		int max = bd->props.max_brightness;
-		gma_backlight_set(dev, bclp * max / 255);
-	}
+	gma_backlight_set(dev, bclp * bd->props.max_brightness / 255);
 
 	asle->cblv = (bclp * 0x64) / 0xff | ASLE_CBLV_VALID;