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/vct_platinumavc_small_defconfig b/configs/vct_platinumavc_small_defconfig
index 0d8cd07..e7b2b1b 100644
--- a/configs/vct_platinumavc_small_defconfig
+++ b/configs/vct_platinumavc_small_defconfig
@@ -20,6 +20,7 @@
 # CONFIG_CMD_MISC is not set
 # CONFIG_ISO_PARTITION is not set
 CONFIG_ENV_IS_IN_FLASH=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 # CONFIG_NET is not set
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_FLASH_CFI_DRIVER=y