[ddk] Remove driver bind() cookie and unbind() callback

Also removed "owner" and "owner_cookie" from internal zx_device_t struct

Adjusted intel-hda audio drivers to create devices to hold driver context
rather than using the driver bind cookie.

Change-Id: I0eca7f6fa3b155be71843291812e7aa9fea5bf55

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[dev] Ethertap driver

Allows creation of ethermac devices that read/write to a channel instead
of hardware.

Change-Id: I7455e5a189bf99058f18f0aa5db9e5684e79776f