mx7ulp_evk: 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: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/mx7ulp_evk_defconfig b/configs/mx7ulp_evk_defconfig
index d630113..0470fbd 100644
--- a/configs/mx7ulp_evk_defconfig
+++ b/configs/mx7ulp_evk_defconfig
@@ -4,6 +4,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx7ulp-evk"
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/mx7ulp_evk/imximage.cfg"
 CONFIG_HUSH_PARSER=y
+CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y