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/taurus_defconfig b/configs/taurus_defconfig
index 027ae66..fcb9030 100644
--- a/configs/taurus_defconfig
+++ b/configs/taurus_defconfig
@@ -58,6 +58,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="at91sam9g20-taurus"
 CONFIG_SPL_OF_PLATDATA=y
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SPL_DM=y
 CONFIG_BLK=y
 CONFIG_CLK=y