boards: Use a better way to find csk.board.cmake
* Use variable ZEPHYR_CSK_MODULE_DIR to locate csk folder path. Signed-off-by: 徐宪辉 <xhxu@listenai.com>
* Use variable ZEPHYR_CSK_MODULE_DIR to locate csk folder path. Signed-off-by: 徐宪辉 <xhxu@listenai.com>