board: nitrogen6x: migrate to CONFIG_DM_VIDEO

Enable driver model for Video to remove compiler warning.
To enable display, issue

setenv stdout serial,vidconsole;

Add CONFIG_DM_VIDEO to all defconfigs whose board is
nitrogen6x.
        mx6qsabrelite_defconfig
        nitrogen6dl2g_defconfig
        nitrogen6dl_defconfig
        nitrogen6q2g_defconfig
        nitrogen6q_defconfig
        nitrogen6s1g_defconfig
	nitrogen6s_defconfig

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Tested-by: Anatolij Gustschin <agust@denx.de>
diff --git a/configs/nitrogen6dl_defconfig b/configs/nitrogen6dl_defconfig
index 0de09d4..16ef289 100644
--- a/configs/nitrogen6dl_defconfig
+++ b/configs/nitrogen6dl_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX6=y
 CONFIG_SYS_TEXT_BASE=0x17800000
+CONFIG_SYS_MALLOC_F_LEN=0x4000
 CONFIG_ENV_SIZE=0x2000
 CONFIG_ENV_OFFSET=0xC0000
 CONFIG_ENV_SECT_SIZE=0x2000
@@ -9,7 +10,6 @@
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_CMD_HDMIDETECT=y
 CONFIG_AHCI=y
-# CONFIG_SYS_MALLOC_F is not set
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6dl.cfg,MX6DL,DDR_MB=1024"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_PREBOOT=y
@@ -74,6 +74,6 @@
 CONFIG_CI_UDC=y
 CONFIG_USB_ETHER=y
 CONFIG_USB_ETH_CDC=y
+CONFIG_DM_VIDEO=y
+CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_VIDEO_IPUV3=y
-CONFIG_VIDEO=y
-# CONFIG_VIDEO_SW_CURSOR is not set