video: fsl_dcu_fb: fix framebuffer to the end of memory

Fix the framebuffer location to the very end of the available memory.
This allows to remove the area from available memory for the kernel,
which in turn allows to display the splash screen through the Linux
kernel boot process.

Ideas has been taken from the sunxi display driver, e.g.
20779ec3a5 ("sunxi: video: Dynamically reserve framebuffer memory")

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 6aab8af..d1b017c 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -402,6 +402,14 @@
 	 This enables support for Freescale Display Control Unit (DCU4)
 	 module found on Freescale Vybrid and QorIQ family of SoCs.
 
+config VIDEO_FSL_DCU_MAX_FB_SIZE_MB
+	int "Freescale DCU framebuffer size"
+	depends on VIDEO_FSL_DCU_FB
+	default 4194304
+	help
+	 Set maximum framebuffer size to be used for Freescale Display
+	 Controller Unit (DCU4).
+
 config VIDEO_ROCKCHIP
 	bool "Enable Rockchip video support"
 	depends on DM_VIDEO