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/configs/ls1021atwr_qspi_defconfig b/configs/ls1021atwr_qspi_defconfig
index 46f7e26..548d574 100644
--- a/configs/ls1021atwr_qspi_defconfig
+++ b/configs/ls1021atwr_qspi_defconfig
@@ -50,3 +50,4 @@
 CONFIG_USB_XHCI_DWC3=y
 CONFIG_USB_STORAGE=y
 # CONFIG_VIDEO_SW_CURSOR is not set
+CONFIG_VIDEO_FSL_DCU_FB=y