lib: utils/serial: Add support for Gaisler APBUART

This patch adds support for the UART used by the NOEL-V processor.

Cobham Gaisler's NOEL-V RISC-V processor IP is available under GPL
and commercial license and is described in more detail at
https://www.gaisler.com/noelv.

Signed-off-by: Daniel Cederman <cederman@gaisler.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/sbi_utils/serial/gaisler-uart.h

@@ -0,0 +1,17 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Cobham Gaisler AB.
+ *
+ * Authors:
+ *   Daniel Cederman <cederman@gaisler.com>
+ */
+
+#ifndef __SERIAL_GAISLER_APBUART_H__
+#define __SERIAL_GAISLER_APBUART_H__
+
+#include <sbi/sbi_types.h>
+
+int gaisler_uart_init(unsigned long base, u32 in_freq, u32 baudrate);
+
+#endif