[NETLINK]: Switch cb_lock spinlock to mutex and allow to override it

Switch cb_lock to mutex and allow netlink kernel users to override it
with a subsystem specific mutex for consistent locking in dump callbacks.
All netlink_dump_start users have been audited not to rely on any
side-effects of the previously used spinlock.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/audit.c b/kernel/audit.c
index 80a7457..4e9d208 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -795,7 +795,7 @@
 	printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 	       audit_default ? "enabled" : "disabled");
 	audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,
-					   THIS_MODULE);
+					   NULL, THIS_MODULE);
 	if (!audit_sock)
 		audit_panic("cannot initialize netlink socket");
 	else