video: add an option for video simplefb via DT

Add an option to indicate that the video driver should setup a SimpleFB
node that passes the video framebuffer initialized by U-Boot to the
operating system kernel.

Currently only the Allwinner DE driver uses this option, and the
definition of this option in the sunxi-common.h config header is
converted to an imply of this option from CONFIG_VIDEO_SUNXI.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/mach-sunxi/Kconfig

@@ -615,6 +615,7 @@ config VIDEO_SUNXI
 	depends on !MACH_SUN9I
 	depends on !MACH_SUN50I
 	select VIDEO
+	imply VIDEO_DT_SIMPLEFB
 	default y
 	---help---
 	Say Y here to add support for using a cfb console on the HDMI, LCD

drivers/video/Kconfig

@@ -650,4 +650,12 @@ config VIDEO_SIMPLE
 	  before u-boot starts, and u-boot will simply render to the pre-
 	  allocated frame buffer surface.
 
+config VIDEO_DT_SIMPLEFB
+	bool "Enable SimpleFB support for passing framebuffer to OS"
+	help
+	  Enables the code to pass the framebuffer to the kernel as a
+	  simple framebuffer in the device tree.
+	  The video output is initialized by U-Boot, and kept by the
+	  kernel.
+
 endmenu

include/configs/sunxi-common.h

@@ -275,9 +275,6 @@ extern int soft_i2c_gpio_scl;
  */
 #define CONFIG_SUNXI_MAX_FB_SIZE (16 << 20)
 
-/* Do we want to initialize a simple FB? */
-#define CONFIG_VIDEO_DT_SIMPLEFB
-
 #define CONFIG_VIDEO_LOGO
 #define CONFIG_VIDEO_STD_TIMINGS
 #define CONFIG_I2C_EDID