video: add config option to skip framebuffer clear

The use-case is that the thing that loaded u-boot already put a splash
image on screen.  And we want to preserve that until grub boot menu
takes over.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 5505ee6..7ba7b58 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -119,6 +119,14 @@
 	 better in low-light situations or to reduce eye strain in some
 	 cases.
 
+config NO_FB_CLEAR
+	bool "Skip framebuffer clear"
+	help
+	  If firmware (whatever loads u-boot) has already put a splash image
+	  on screen, you might want to preserve it until whatever u-boot
+	  loads takes over the screen.  This, for example, can be used to
+	  keep splash image on screen until grub graphical boot menu starts.
+
 source "drivers/video/fonts/Kconfig"
 
 config VIDCONSOLE_AS_LCD