Add chip ID funcitions for Shenzhou and Cloudctrl boards; Extened NSH ifconfig...

Add chip ID funcitions for Shenzhou and Cloudctrl boards; Extened NSH ifconfig command and improve DHCPC -- All from Darcy Gong

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5393 42af7a65-404d-4744-a932-0658087f49c3