arm: zynq: Enable alternative memory test

Enable alternative memory test for zynq platforms.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/xilinx_zynq_virt_defconfig b/configs/xilinx_zynq_virt_defconfig
index 5da7440..54c3076 100644
--- a/configs/xilinx_zynq_virt_defconfig
+++ b/configs/xilinx_zynq_virt_defconfig
@@ -24,6 +24,7 @@
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_THOR_DOWNLOAD=y
 CONFIG_CMD_MEMTEST=y
+CONFIG_SYS_ALT_MEMTEST=y
 CONFIG_SYS_MEMTEST_START=0x00000000
 CONFIG_SYS_MEMTEST_END=0x00001000
 CONFIG_CMD_DFU=y