mx7_common: use Kconfig for ARMv7 non-secure mode

Use existing Kconfig symbols to let the user configure whether to
build a U-Boot with non-secure mode support or not. This also allows
to enable virtualization extension easily.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/configs/warp7_defconfig b/configs/warp7_defconfig
index 3770669..5a68998 100644
--- a/configs/warp7_defconfig
+++ b/configs/warp7_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX7=y
 CONFIG_TARGET_WARP7=y
+# CONFIG_ARMV7_VIRT is not set
 CONFIG_IMX_RDC=y
 CONFIG_IMX_BOOTAUX=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/warp7/imximage.cfg"