video: fsl_dcu_fb: add DM_VIDEO support

Extend the driver to build with DM_VIDEO enabled. DTS files
must additionally include 'u-boot,dm-pre-reloc' property in
soc and child nodes to enable driver binding to fsl_dcu_fb device.

Currently display timings aren't obtained from DT.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index c3781b1..261fa98 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -484,7 +484,7 @@
 
 config VIDEO_FSL_DCU_FB
 	bool "Enable Freescale Display Control Unit"
-	depends on VIDEO
+	depends on VIDEO || DM_VIDEO
 	help
 	 This enables support for Freescale Display Control Unit (DCU4)
 	 module found on Freescale Vybrid and QorIQ family of SoCs.