Convert CONFIG_VIDEO to Kconfig

This converts the following to Kconfig:
   CONFIG_VIDEO

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>
diff --git a/configs/riotboard_defconfig b/configs/riotboard_defconfig
index 652b13f..404d25e 100644
--- a/configs/riotboard_defconfig
+++ b/configs/riotboard_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX6=y
 CONFIG_TARGET_EMBESTMX6BOARDS=y
+CONFIG_VIDEO=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6s1g.cfg,MX6S,DDR_MB=1024,ENV_IS_IN_MMC"
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y