riscv: Add AST2700 SoC initial platform support

AST2700 SoCs integrates a Ibex 32-bits RISC-V core as the boot MCU
for the first stage bootloader execution, namely SPL.

This patch implements the preliminary base to successfully run SPL
on this RV32-based MCU to the console banner message.

Signed-off-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

include/configs/ibex_ast2700.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) Aspeed Technology Inc.
+ */
+
+#ifndef __CONFIG_H
+#define __CONFIG_H
+
+#define CFG_SYS_UBOOT_BASE	CONFIG_TEXT_BASE
+#define CFG_SYS_SDRAM_BASE	0x80000000
+
+#endif	/* __CONFIG_H */