[PATCH] drm/panel-edp: modify Kconfig to prevent build error

[Randy Dunlap]

When CONFIG_DRM_KMS_HELPER=m and CONFIG_DRM_PANEL_EDP=y,
there is a build error in gpu/drm/panel/panel-edp.o:

arm-linux-gnueabi-ld: drivers/gpu/drm/panel/panel-edp.o: in function `panel_edp_probe':
panel-edp.c:(.text+0xf38): undefined reference to `drm_panel_dp_aux_backlight'

Fix this by limiting DRM_PANEL_DEP by the value of the DRM_KMS_HELPER
symbol.

Fixes: 5f04e7ce392d ("drm/panel-edp: Split eDP panels out of panel-simple")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
---
 drivers/gpu/drm/panel/Kconfig |    1 +
 1 file changed, 1 insertion(+)

--- linux-next-20211117.orig/drivers/gpu/drm/panel/Kconfig
+++ linux-next-20211117/drivers/gpu/drm/panel/Kconfig
@@ -104,6 +104,7 @@ config DRM_PANEL_EDP
 	depends on OF
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on PM
+	depends on DRM_KMS_HELPER
 	select VIDEOMODE_HELPERS
 	select DRM_DP_AUX_BUS
 	help