drm/panel: Add simple panel support

Add a driver for simple panels. Such panels can have a regulator that
provides the supply voltage and a separate GPIO to enable the panel.
Optionally the panels can have a backlight associated with them so it
can be enabled or disabled according to the panel's power management
mode.

Support is added for two panels: An AU Optronics 10.1" WSVGA and a
Chunghwa Picture Tubes 10.1" WXGA panel.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/panel/Kconfig

@@ -3,3 +3,17 @@ config DRM_PANEL
 	depends on DRM
 	help
 	  Panel registration and lookup framework.
+
+menu "Display Panels"
+	depends on DRM_PANEL
+
+config DRM_PANEL_SIMPLE
+	tristate "support for simple panels"
+	depends on OF
+	help
+	  DRM panel driver for dumb panels that need at most a regulator and
+	  a GPIO to be powered up. Optionally a backlight can be attached so
+	  that it can be automatically turned off when the panel goes into a
+	  low power state.
+
+endmenu