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/pengwyn_defconfig b/configs/pengwyn_defconfig
index 4ac03dc..ab88d06 100644
--- a/configs/pengwyn_defconfig
+++ b/configs/pengwyn_defconfig
@@ -44,6 +44,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=omap2-nand.0:512k(SPL),512k(SPL.backup1),512k(SPL.backup2),512k(SPL.backup3),1536k(u-boot),512k(u-boot-spl-os),512k(u-boot-env),5m(kernel),-(rootfs)"
 CONFIG_CMD_DIAG=y
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_NAND=y
 CONFIG_DRIVER_TI_CPSW=y