Bluetooth: host: Fix L2CAP reconfigure response with invalid MTU

TSE18813 clarified IUT behavior and rejecting reconfiguration which
would result in MTU decrease is enough. There is no need to disconnect
L2CAP channel(s).

This was affecting L2CAP/ECFC/BI-03-C qualification test case
(TCRL 2022-2).

Signed-off-by: Szymon Janc <[email protected]>
(cherry picked from commit 266394d)

Author: sjanc

subsys/bluetooth/host/l2cap.c

@@ -1298,15 +1298,10 @@ static void le_ecred_reconf_req(struct bt_l2cap *l2cap, uint8_t ident,
 			continue;
 		}
 
-		/* If the MTU value is decreased for any of the included
-		 * channels, then the receiver shall disconnect all
-		 * included channels.
-		 */
 		if (BT_L2CAP_LE_CHAN(chan)->tx.mtu > mtu) {
 			BT_ERR("chan %p decreased MTU %u -> %u", chan,
 			       BT_L2CAP_LE_CHAN(chan)->tx.mtu, mtu);
 			result = BT_L2CAP_RECONF_INVALID_MTU;
-			bt_l2cap_chan_disconnect(chan);
 			goto response;
 		}