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/corvus_defconfig b/configs/corvus_defconfig
index 56c6123..7683a80 100644
--- a/configs/corvus_defconfig
+++ b/configs/corvus_defconfig
@@ -41,6 +41,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_DEFAULT_DEVICE_TREE="at91sam9g45-corvus"
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_BLK=y
 CONFIG_CLK=y
 CONFIG_CLK_AT91=y