aspeed: Add AST2600 platform support

Add low level platform initialization for the AST2600 SoC.
The 2-stage booting with U-Boot SPL are leveraged to support
different booting mode.

However, currently the patch supports only the booting from
memory-mapped SPI flash.

Signed-off-by: Chia-Wei, Wang <chiawei_wang@aspeedtech.com>
Reviewed-by: Ryan Chen <ryan_chen@aspeedtech.com>
diff --git a/board/aspeed/evb_ast2600/Kconfig b/board/aspeed/evb_ast2600/Kconfig
new file mode 100644
index 0000000..42008cd
--- /dev/null
+++ b/board/aspeed/evb_ast2600/Kconfig
@@ -0,0 +1,12 @@
+if TARGET_EVB_AST2600
+
+config SYS_BOARD
+	default "evb_ast2600"
+
+config SYS_VENDOR
+	default "aspeed"
+
+config SYS_CONFIG_NAME
+	default "evb_ast2600"
+
+endif