Bluetooth: SMP: Fix key type in security request

Required key is LTK not IRK.

Change-Id: Ibbb27b08867d88e74b30ccb592994f169b455bf9
Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 5d90843..a5bcc0f 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -688,7 +688,7 @@
 
 	BT_DBG("\n");
 
-	keys = bt_keys_find(BT_KEYS_IRK, &conn->dst);
+	keys = bt_keys_find(BT_KEYS_LTK, &conn->dst);
 	if (!keys) {
 		goto pair;
 	}