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/arch/arm/cpu/armv7/mx7/Kconfig b/arch/arm/cpu/armv7/mx7/Kconfig
index ecfa4a2..dd51384 100644
--- a/arch/arm/cpu/armv7/mx7/Kconfig
+++ b/arch/arm/cpu/armv7/mx7/Kconfig
@@ -3,6 +3,8 @@
 config MX7
 	bool
 	select ROM_UNIFIED_SECTIONS
+	select CPU_V7_HAS_VIRT
+	select CPU_V7_HAS_NONSEC
 	default y
 
 config MX7D