Convert CONFIG_FSL_DCU_FB to Kconfig

Rename CONFIG_FSL_DCU_FB to CONFIG_VIDEO_FSL_DCU_FB
and convert it to Kconfig.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Reviewed-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Alison Wang <alison.wang@nxp.com>
diff --git a/board/freescale/ls1021atwr/Makefile b/board/freescale/ls1021atwr/Makefile
index 5238b15..d9a2f52 100644
--- a/board/freescale/ls1021atwr/Makefile
+++ b/board/freescale/ls1021atwr/Makefile
@@ -5,5 +5,5 @@
 #
 
 obj-y += ls1021atwr.o
-obj-$(CONFIG_FSL_DCU_FB) += dcu.o
+obj-$(CONFIG_VIDEO_FSL_DCU_FB) += dcu.o
 obj-$(CONFIG_ARMV7_PSCI) += psci.o