caif: Use rcu_read_lock in CAIF mux layer.

Replace spin_lock with rcu_read_lock when accessing lists to layers
and cache. While packets are in flight rcu_read_lock should not be held,
instead ref-counters are used in combination with RCU.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/caif/cffrml.c b/net/caif/cffrml.c
index 2423fed..f4b8892 100644
--- a/net/caif/cffrml.c
+++ b/net/caif/cffrml.c
@@ -145,3 +145,11 @@
 	if (layr->up->ctrlcmd)
 		layr->up->ctrlcmd(layr->up, ctrl, layr->id);
 }
+
+void cffrml_put(struct cflayer *layr)
+{
+}
+
+void cffrml_hold(struct cflayer *layr)
+{
+}