Fix log level - requesting MTU is not error

Test: compilation
Change-Id: Idf99af22cf4d29f6fb3da08e86e36b3394617c4f
diff --git a/stack/gatt/gatt_sr.cc b/stack/gatt/gatt_sr.cc
index c7bbe4a..35bd993 100644
--- a/stack/gatt/gatt_sr.cc
+++ b/stack/gatt/gatt_sr.cc
@@ -741,7 +741,7 @@
   else
     tcb.payload_size = mtu;
 
-  LOG(ERROR) << "MTU request PDU with MTU size " << +tcb.payload_size;
+  LOG(INFO) << "MTU request PDU with MTU size " << +tcb.payload_size;
 
   l2cble_set_fixed_channel_tx_data_length(tcb.peer_bda, L2CAP_ATT_CID,
                                           tcb.payload_size);