hv: clean up function definitions in vuart.h

seperate the function definitions into debug/release directories
to better distinguish debug/release libraries

Tracked-On: #861
Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/release/vuart.c

@@ -0,0 +1,17 @@
+/*
+ * Copyright (C) 2018 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <hypervisor.h>
+
+void vuart_init(__unused struct acrn_vm *vm) {}
+
+struct acrn_vuart *vuart_console_active(void)
+{
+	return NULL;
+}
+
+void vuart_console_tx_chars(__unused struct acrn_vuart *vu) {}
+void vuart_console_rx_chars(__unused struct acrn_vuart *vu) {}