dm: backlight: Add a driver for GPIO backlight

Add a driver for GPIO backlights.
It understands the standard device tree binding.
It can be used with simple-panel when PWM is not necessary.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index fe34da0..40a656e 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -25,6 +25,16 @@
 	  it understands the standard device tree
 	  (leds/backlight/pwm-backlight.txt)
 
+config BACKLIGHT_GPIO
+	bool "Generic GPIO based Backlight Driver"
+	depends on DM_VIDEO
+	help
+	  If you have a LCD backlight adjustable by GPIO, say Y to enable
+	  this driver.
+	  This driver can be used with "simple-panel" and
+	  it understands the standard device tree
+	  (leds/backlight/gpio-backlight.txt)
+
 config VIDEO_BPP8
 	bool "Support 8-bit-per-pixel displays"
 	depends on DM_VIDEO