kobject: Export kobj_ns_grab_current() and kobj_ns_drop()

Make it possible to call these two functions from a kernel module.
Note: despite their name, these two functions can be used meaningfully
independent of kobjects. A later patch will add calls to these
functions from the SRP driver because this patch series modifies the
SRP driver such that it can hold a reference to a namespace that can
last longer than the lifetime of the process through which the
namespace reference was obtained.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

lib/kobject.c

@@ -1039,6 +1039,7 @@ void *kobj_ns_grab_current(enum kobj_ns_type type)
 
 	return ns;
 }
+EXPORT_SYMBOL_GPL(kobj_ns_grab_current);
 
 const void *kobj_ns_netlink(enum kobj_ns_type type, struct sock *sk)
 {
@@ -1074,3 +1075,4 @@ void kobj_ns_drop(enum kobj_ns_type type, void *ns)
 		kobj_ns_ops_tbl[type]->drop_ns(ns);
 	spin_unlock(&kobj_ns_type_lock);
 }
+EXPORT_SYMBOL_GPL(kobj_ns_drop);