arm: imx-common: add SECURE_BOOT option to Kconfig

So the option can easily be selected through menuconfig.
Signed-off-by: NGary Bisson <gary.bisson@boundarydevices.com>

arch/arm/imx-common/Kconfig

@@ -17,3 +17,10 @@ config IMX_BOOTAUX
 	depends on ARCH_MX7 || ARCH_MX6
 	help
 	  bootaux [addr] to boot auxiliary core.
+
+config SECURE_BOOT
+	bool "Support i.MX HAB features"
+	depends on ARCH_MX7 || ARCH_MX6 || ARCH_MX5
+	help
+	  This option enables the support for secure boot (HAB).
+	  See doc/README.mxc_hab for more details.