MIPS: Ingenic: Add YSH & ATIL CU Neo board support.

Add a device tree and a defconfig for the Ingenic X1830 based
YSH & ATIL CU Neo board.

Tested-by: 周正 (Zhou Zheng) <sernia.zhou@foxmail.com>
Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>