board/olpc: move BACKLIGHT_CLASS_DEVICE up to common config

Both machines need it.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

board/olpc/linux.config

@@ -45,6 +45,7 @@ CONFIG_DRM_PANEL_SIMPLE=m
 CONFIG_FRAMEBUFFER_CONSOLE=y
 CONFIG_FB_SIMPLE=y
 CONFIG_LCD_CLASS_DEVICE=y
+CONFIG_BACKLIGHT_CLASS_DEVICE=y
 CONFIG_SOUND=y
 CONFIG_SND=y
 CONFIG_USB=y

board/olpc/xo-1.75/linux.config

@@ -19,7 +19,6 @@ CONFIG_DRM_ARMADA=y
 CONFIG_DRM_DISPLAY_CONNECTOR=m
 CONFIG_DRM_SIMPLE_BRIDGE=m
 CONFIG_DRM_ETNAVIV=m
-CONFIG_BACKLIGHT_CLASS_DEVICE=y
 CONFIG_USB_EHCI_MV=y
 CONFIG_MMC_SDHCI_PXAV3=y
 CONFIG_OLPC_XO175=y