Bluetooth: Convert RFCOMM spinlocks into mutexes

Enabling CONFIG_DEBUG_ATOMIC_SLEEP has shown that some rfcomm functions
acquiring spinlocks call sleeping locks further in the chain.  Converting
the offending spinlocks into mutexes makes sleeping safe.

Signed-off-by: Libor Pechacek <lpechacek@suse.cz>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index 633ccee..05c609b 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -307,7 +307,7 @@
 	setup_timer(&d->timer, rfcomm_dlc_timeout, (unsigned long)d);
 
 	skb_queue_head_init(&d->tx_queue);
-	spin_lock_init(&d->lock);
+	mutex_init(&d->lock);
 	atomic_set(&d->refcnt, 1);
 
 	rfcomm_dlc_clear_state(d);