Migrate CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG to Kconfig

Convert CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG to Kconfig

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Petr Vorel <petr.vorel@gmail.com>
Reviewed-by: Petr Vorel <petr.vorel at gmail.com>
diff --git a/configs/s5pc210_universal_defconfig b/configs/s5pc210_universal_defconfig
index 5014216..62b585d 100644
--- a/configs/s5pc210_universal_defconfig
+++ b/configs/s5pc210_universal_defconfig
@@ -25,6 +25,7 @@
 CONFIG_CMD_EXT4_WRITE=y
 CONFIG_MTDPARTS_DEFAULT="mtdparts=samsung-onenand:128k(s-boot),896k(bootloader),256k(params),2816k(config),8m(csa),7m(kernel),1m(log),12m(modem),60m(qboot),-(UBI)"
 CONFIG_OF_CONTROL=y
+CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
 CONFIG_DFU_MMC=y
 CONFIG_SYS_I2C_S3C24X0=y
 CONFIG_DM_MMC=y