ASoC: SOF: Intel: Do not process IPC reply before firmware boot

ASoC: SOF: Intel: Do not process IPC reply before firmware boot

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

By mistake a developer managed to create a 'corrupted' IPC4 firmware image which
loaded fine to the DSP and after boot it sent an IPC reply before we would have
received the FW_READY message.
It turned out that the image was an IPC3 firmware and the IPC reply was the IPC3
FW_READY notification message which got understood as an IPC4 reply message due
to the difference between the two IPC mechanism.

This caused a NULL pointer dereference since the reply memory will be allocated
after the FW_READY message.

To make sure this will not bite again, skip any spurious reply messages before
the FW_READY.