armv7: ls1021aiot: Move CONFIG_CMD_BOOTZ to Kconfig

CONFIG_CMD_BOOTZ symbol does not work in board config file
anymore, so fix this by moving it to Kconfig.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/configs/ls1021aiot_qspi_defconfig b/configs/ls1021aiot_qspi_defconfig
index 04d3658..46aa7bf 100644
--- a/configs/ls1021aiot_qspi_defconfig
+++ b/configs/ls1021aiot_qspi_defconfig
@@ -3,6 +3,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="ls1021a-iot-duart"
 CONFIG_SYS_EXTRA_OPTIONS="QSPI_BOOT"
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GPT=y
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_FAT=y