ASoC: SOF: Rework the firmware ready message handling

Merge series from Peter Ujfalusi <peter.ujfalusi@linux.intel.com>:

The firmware ready (fw_ready) message is sent by the firmware to notify the host
that it has been booted up and caries additional information about it's
configuration.
All of this is IPC specific, the message itself is IPC version specific and the
information itself also.

Move the code to handle the fw_ready message under ipc3.c since the parsing and
interpretation is IPC specific.

A followup series is going to take care of the rest of the loader.c to make it
IPC agnostic.