ns: move ns type into struct ns_common

It's misplaced in struct proc_ns_operations and ns->ops might be NULL if
the namespace is compiled out but we still want to know the type of the
namespace for the initial namespace struct.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

init/version-timestamp.c

@@ -8,6 +8,7 @@
 #include <linux/utsname.h>
 
 struct uts_namespace init_uts_ns = {
+	.ns.ns_type = ns_common_type(&init_uts_ns),
 	.ns.__ns_ref = REFCOUNT_INIT(2),
 	.name = {
 		.sysname	= UTS_SYSNAME,