Convert CONFIG_NAND_MXS to Kconfig

This converts CONFIG_NAND_MXS to Kconfig.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/configs/cm_fx6_defconfig b/configs/cm_fx6_defconfig
index c9c2fdf..5349398 100644
--- a/configs/cm_fx6_defconfig
+++ b/configs/cm_fx6_defconfig
@@ -20,9 +20,7 @@
 CONFIG_SPL=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x80
 CONFIG_SPL_I2C_SUPPORT=y
-CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="CM-FX6 # "
-CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_XIMG is not set
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_EEPROM=y
@@ -34,20 +32,13 @@
 # CONFIG_CMD_LOADB is not set
 # CONFIG_CMD_LOADS is not set
 CONFIG_CMD_MMC=y
-CONFIG_CMD_NAND=y
 CONFIG_CMD_SATA=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_USB=y
 # CONFIG_CMD_SETEXPR is not set
-CONFIG_CMD_DHCP=y
-CONFIG_CMD_PING=y
 CONFIG_CMD_BMP=y
 CONFIG_CMD_CACHE=y
-CONFIG_CMD_EXT2=y
-CONFIG_CMD_EXT4=y
 CONFIG_CMD_EXT4_WRITE=y
-CONFIG_CMD_FAT=y
-CONFIG_CMD_FS_GENERIC=y
 CONFIG_CMD_MTDPARTS=y
 CONFIG_MTDIDS_DEFAULT="nor0=spi0.0"
 CONFIG_MTDPARTS_DEFAULT="mtdparts=spi0.0:768k(uboot),256k(uboot-environment),-(reserved)"
@@ -56,6 +47,8 @@
 CONFIG_DWC_AHSATA=y
 CONFIG_DM_KEYBOARD=y
 CONFIG_DM_MMC=y
+CONFIG_NAND=y
+CONFIG_NAND_MXS=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_ATMEL=y
 CONFIG_SPI_FLASH_EON=y