configs: Remove unused IMX_NAND symbol

The symbol CONFIG_IMX_NAND is not referenced in the code, remove it.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/colibri-imx6ull_defconfig b/configs/colibri-imx6ull_defconfig
index d0e85b1..0d46dda 100644
--- a/configs/colibri-imx6ull_defconfig
+++ b/configs/colibri-imx6ull_defconfig
@@ -12,7 +12,6 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx6ull-colibri"
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_FIT=y
-CONFIG_SYS_EXTRA_OPTIONS="IMX_NAND"
 CONFIG_BOOTDELAY=1
 # CONFIG_USE_BOOTCOMMAND is not set
 CONFIG_USE_PREBOOT=y
diff --git a/configs/colibri_vf_defconfig b/configs/colibri_vf_defconfig
index d8f44c2..05413c0 100644
--- a/configs/colibri_vf_defconfig
+++ b/configs/colibri_vf_defconfig
@@ -13,7 +13,6 @@
 CONFIG_TARGET_COLIBRI_VF=y
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
 CONFIG_SYS_LOAD_ADDR=0x80008000
-CONFIG_SYS_EXTRA_OPTIONS="IMX_NAND"
 CONFIG_BOOTDELAY=1
 CONFIG_USE_PREBOOT=y
 CONFIG_PREBOOT="setenv fdtfile ${soc}-colibri-${fdt_board}.dtb"