arch/riscv: Refactor move toolchain option to arch's toolchain dir. [3/5]

PD#SWPL-68240

Problem:
Refactor move toolchain switch to arch's toolchain dir.

Solution:
Refactor move toolchain switch to arch's toolchain dir.

Verify:
N/A

Change-Id: Iedb9922beee7fe7f3e8b4c35203d34617899df61
Signed-off-by: xiaohu.huang <xiaohu.huang@amlogic.com>
diff --git a/toolchain/Kconfig b/toolchain/Kconfig
new file mode 100644
index 0000000..9e180aa
--- /dev/null
+++ b/toolchain/Kconfig
@@ -0,0 +1,15 @@
+# Copyright (c) 2021-2022 Amlogic, Inc. All rights reserved.
+
+# SPDX-License-Identifier: MIT
+
+choice TOOLCHAIN
+	bool "Toolchain selection"
+	default TOOLCHAIN_GCC
+	help
+	  "Select toolchain"
+
+	config TOOLCHAIN_GCC
+	bool "GCC"
+	help
+	  "Select GCC toolchain"
+endchoice