asoc: JZ4750: Make alsa sound work.

Sound is working in principle, but there are occasional kernel panics
on Dingoo A380 due to invalid pointer. Curiously, Ritmix RZX-50 doesn't
have them.

TODO:
 - eliminate sound pops on codec activation
 - check routes

This is a squashed commit from jz-3.15-asoc branch up to 2014-11-26