system/init: add option for no init system

Can be usefull if a local package provides an init procedure.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

target/generic/Config.in

@@ -64,6 +64,9 @@ comment 'systemd requires largefile, wchar, IPv6, threads and udev support'
 		     BR2_INET_IPV6 && BR2_TOOLCHAIN_HAS_THREADS && \
 		     BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_UDEV)
 
+config BR2_INIT_NONE
+	bool "None"
+
 endchoice
 
 config BR2_ROOTFS_DEVICE_TABLE