AMD/bettong: Add missing uart.c for UART

Change-Id: Ie49732c6874f2b443e314eb3412ddee054d9c0bb
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: https://review.coreboot.org/12669
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/southbridge/amd/pi/hudson/uart.c

@@ -0,0 +1,26 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2015 Advanced Micro Devices, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <console/uart.h>
+
+uintptr_t uart_platform_base(int idx)
+{
+	return (uintptr_t)(0xFEDC6000 + 0x2000 * (idx & 1));
+}
+
+unsigned int uart_platform_refclk(void)
+{
+	return 48000000;
+}