Bluetooth: SMP: Fix compilation with debugs enabled

This fix following compilation error if CONFIG_BLUETOOTH_DEBUG_SMP
is defined:

In file included from net/bluetooth/smp.c:44:0:
net/bluetooth/smp.c: In function 'bt_smp_irk_matches':
net/bluetooth/smp.c:681:31: error: 'val' undeclared
    (first use in this function)
  BT_DBG("IRK %s bdaddr %s", h(val, 16), bt_addr_str(addr));

Change-Id: I3350620f1f7dc929b949b4483178df66dde55198
Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index c27b7c3..0f5997b 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -678,7 +678,7 @@
 	uint8_t hash[3];
 	int err;
 
-	BT_DBG("IRK %s bdaddr %s", h(val, 16), bt_addr_str(addr));
+	BT_DBG("IRK %s bdaddr %s", h(irk, 16), bt_addr_str(addr));
 
 	err = smp_ah(irk, addr->val + 3, hash);
 	if (err) {