video: Move and rename DM_HX8238D option

This is actually a panel, not a video device. Rename the option, move it
into the right place and make it depend on PANEL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 7019b26..5a67354 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -15,7 +15,7 @@
 obj-$(CONFIG_DM_VIDEO) += video-uclass.o vidconsole-uclass.o
 obj-$(CONFIG_DM_VIDEO) += video_bmp.o
 obj-$(CONFIG_PANEL) += panel-uclass.o
-obj-$(CONFIG_DM_PANEL_HX8238D) += hx8238d.o
+obj-$(CONFIG_PANEL_HX8238D) += hx8238d.o
 obj-$(CONFIG_SIMPLE_PANEL) += simple_panel.o
 
 obj-$(CONFIG_VIDEO_LOGO) += u_boot_logo.o