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>
diff --git a/board/aspeed/ibex_ast2700/Kconfig b/board/aspeed/ibex_ast2700/Kconfig
new file mode 100644
index 0000000..469cea5
--- /dev/null
+++ b/board/aspeed/ibex_ast2700/Kconfig
@@ -0,0 +1,21 @@
+if TARGET_ASPEED_AST2700_IBEX
+
+config SYS_BOARD
+	default "ibex_ast2700"
+
+config SYS_VENDOR
+	default "aspeed"
+
+config SYS_CPU
+	default "ast2700"
+
+config SYS_CONFIG_NAME
+	default "ibex_ast2700"
+
+config BOARD_SPECIFIC_OPTIONS
+	def_bool y
+	select RISCV_AST2700
+	select SUPPORT_SPL
+	imply SPL_DRIVERS_MISC
+
+endif