defconfigs: Migrate CONFIG_SYS_REDUNDAND_ENVIRONMENT

Move this symbol to Kconfig.  As part of this we can drop a UBI-specific
symbol that was a stop-gap for not having this particular symbol in
Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/gwventana_emmc_defconfig b/configs/gwventana_emmc_defconfig
index 651d3396..30f246b 100644
--- a/configs/gwventana_emmc_defconfig
+++ b/configs/gwventana_emmc_defconfig
@@ -59,6 +59,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=nand:16m(uboot),1m(env),-(rootfs)"
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_MMC=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_DM=y
 CONFIG_DWC_AHSATA=y
 CONFIG_SUPPORT_EMMC_RPMB=y