New board support and common configuration.

Since all sunxi boards share a very common configuration, there's no point in
setting all parameters, instead source a default configuration and just change
what is different between boards.

Add initlal support for a little noname 7" tablet i've bought from DX.com (They
say it's an A70Xh, fex says k70-v10). Anyway, it cost almost nothing and got a
A20. just short on ram and could have a better screen.