drm/panel: r66451: select CONFIG_DRM_DISPLAY_DP_HELPER

The newly added driver only builds when DRM_DISPLAY_DP_HELPER is enabled:

x86_64-linux-ld: drivers/gpu/drm/panel/panel-visionox-r66451.o: in function `visionox_r66451_enable':
panel-visionox-r66451.c:(.text+0x105): undefined reference to `drm_dsc_pps_payload_pack'

Select both CONFIG_DRM_DISPLAY_DP_HELPER and CONFIG_DRM_DISPLAY_HELPER to
ensure the helper function is always available.

Fixes: a6dfab27 ("drm/panel: Add driver for Visionox r66451 panel")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230719130940.659837-1-arnd@kernel.org

drivers/gpu/drm/panel/Kconfig

@@ -799,6 +799,8 @@ config DRM_PANEL_VISIONOX_R66451
 	depends on OF
 	depends on DRM_MIPI_DSI
 	depends on BACKLIGHT_CLASS_DEVICE
+	select DRM_DISPLAY_DP_HELPER
+	select DRM_DISPLAY_HELPER
 	help
 	  Say Y here if you want to enable support for Visionox
 	  R66451 1080x2340 AMOLED DSI panel.