xilinx: Enable redundant variable handling

Enable this feature by default to be able to work with env import/export
commands which are done in this slightly changed variable format (There is
addtional flag fields in variable file which is changing CRC calculation).

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/xilinx_zynq_virt_defconfig b/configs/xilinx_zynq_virt_defconfig
index bdd6be2..3892a71 100644
--- a/configs/xilinx_zynq_virt_defconfig
+++ b/configs/xilinx_zynq_virt_defconfig
@@ -60,6 +60,7 @@
 CONFIG_ENV_IS_IN_FAT=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y
+CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_NETCONSOLE=y