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/mpc8308_p1m_defconfig b/configs/mpc8308_p1m_defconfig
index cb0da47..68d20b1 100644
--- a/configs/mpc8308_p1m_defconfig
+++ b/configs/mpc8308_p1m_defconfig
@@ -107,6 +107,7 @@
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_FLASH_CFI_DRIVER=y