Adding support for additional i2s card/board drivers

As per a request from koalo, I attach the changes I have made to make the 3.8 i2s card/board drivers work with the 3.10 kernel.  This expands on the existing hifiberry support in 3.10 to include some other common i2s boards.

I have only tested the proto board driver (WM8731 chipset) so I can not vouch for the other drivers.  If you prefer, I am happy to reissue the pull request with just the drivers I have tested.

BBUK