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/socrates_defconfig b/configs/socrates_defconfig
index 2241fbb..99e65f4 100644
--- a/configs/socrates_defconfig
+++ b/configs/socrates_defconfig
@@ -36,6 +36,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_DEFAULT_DEVICE_TREE="socrates"
 CONFIG_ENV_IS_IN_FLASH=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_DM=y
 CONFIG_BLK=y
 CONFIG_DM_I2C=y