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/pcm051_rev3_defconfig b/configs/pcm051_rev3_defconfig
index 8f957e2..6a30fc0 100644
--- a/configs/pcm051_rev3_defconfig
+++ b/configs/pcm051_rev3_defconfig
@@ -39,6 +39,7 @@
 CONFIG_CMD_USB=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_EXT4_WRITE=y
+CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_WINBOND=y