Bluetooth: Host: Modify check for read buffer size v2

Modify the check from checking the feature bit to
checking the command bit. This ensures that we
don't send the read buffer size V2 to a controller
that does not support it.

This also moves the entire ISO init procedure into
a separate function to avoid having a large
ISO-only block in `le_init`.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

subsys/bluetooth/host/hci_core.c

@@ -2776,6 +2776,45 @@ static int le_set_event_mask(void)
 	return bt_hci_cmd_send_sync(BT_HCI_OP_LE_SET_EVENT_MASK, buf, NULL);
 }
 
+#if defined(CONFIG_BT_CONN)
+static int le_init_iso(void)
+{
+	int err;
+	struct net_buf *rsp;
+
+	/* Set Isochronus Channels - Host support */
+	err = le_set_host_feature(BT_LE_FEAT_BIT_ISO_CHANNELS, 1);
+	if (err) {
+		return err;
+	}
+
+	/* Octet 41, bit 5 is read buffer size V2 */
+	if (BT_CMD_TEST(bt_dev.supported_commands, 41, 5)) {
+		/* Read ISO Buffer Size V2 */
+		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_READ_BUFFER_SIZE_V2,
+					   NULL, &rsp);
+		if (err) {
+			return err;
+		}
+		read_buffer_size_v2_complete(rsp);
+	} else {
+		BT_WARN("Read Buffer Size V2 command is not supported."
+			"No ISO buffers will be available");
+
+		/* Read LE Buffer Size */
+		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_READ_BUFFER_SIZE,
+					   NULL, &rsp);
+		if (err) {
+			return err;
+		}
+		le_read_buffer_size_complete(rsp);
+	}
+
+	net_buf_unref(rsp);
+	return 0;
+}
+#endif /* CONFIG_BT_CONN */
+
 static int le_init(void)
 {
 	struct bt_hci_cp_write_le_host_supp *cp_le;
@@ -2801,19 +2840,10 @@ static int le_init(void)
 #if defined(CONFIG_BT_CONN)
 	if (IS_ENABLED(CONFIG_BT_ISO) &&
 	    BT_FEAT_LE_ISO(bt_dev.le.features)) {
-		/* Set Isochronus Channels - Host support */
-		err = le_set_host_feature(BT_LE_FEAT_BIT_ISO_CHANNELS, 1);
-		if (err) {
-			return err;
-		}
-		/* Read ISO Buffer Size V2 */
-		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_READ_BUFFER_SIZE_V2,
-					   NULL, &rsp);
+		err = le_init_iso();
 		if (err) {
 			return err;
 		}
-		read_buffer_size_v2_complete(rsp);
-		net_buf_unref(rsp);
 	} else {
 		/* Read LE Buffer Size */
 		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_READ_BUFFER_SIZE,