Move to new kernel (with adau1761 support)

Add adau1761 drivers and devicetree for Zedboard. For the zc702, adjust the
devicetree to match the new digital audio interface driver.

Known issues:
- ADAU1761 Audio driver takes ages to load, DSP firmware failure.
- Ethernet on zc702 doesn't work (always detects link up)
Add "zed-audio" loader recipe (for Zedboard audio support)

Including zed-audio in your image will load the adau1761 modules at
startup (after configuring the programmable logic). It also places a
/etc/zed_audio.state that can be loaded by alsactl to set the device
mixer for audio output.