Add initial support for Ingenic X1000 SoC and Y&A CU Neo board v6.

[Zhou Yanjie <zhouyanjie@xxxxxxxx>]

v5->v6:
1.Use "stdout-path = "serial2:115200n8"" instead "stdout-path = &uart2" in DT.
2.Remove "console=ttyS2,115200n8" and "CONFIG_CMDLINE_OVERRIDE=y" from defconfg.
3.Add watchdog timer DT node, and update defconfig for watchdog timer.