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/x600_defconfig b/configs/x600_defconfig
index 62ca1d6..c7c9dc4 100644
--- a/configs/x600_defconfig
+++ b/configs/x600_defconfig
@@ -44,6 +44,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=nand:64M(ubi0),64M(ubi1)"
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_FLASH=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_BOOTCOUNT_LIMIT=y
 CONFIG_FPGA_XILINX=y
 CONFIG_FPGA_SPARTAN3=y