All devices under airoha use dts directory under the target, so update the default DEVICE_DTS_DIR. Also set the default DEVICE_DTS based on the SoC name for non-dev boards. Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn> Link: https://github.com/openwrt/openwrt/pull/20190 Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>