ASoC: SOF: prepare code to allocate IPC messages in fw_ready

The fixed maximum size of IPC message does not allow for large
transfers, e.g. for filter data. Currently such messages will
be divided into smaller pieces and sent to firmware in multiple
chunks. For future IPC, this strategy is not suitable.

The maximum IPC message size is limited by host box size which
can be known when firmware is ready, so the fw_ready callback
can allocate IPC messages with platform-specific sizes instead
of the current fixed-size.

To be compatible with released firmware, current platforms will
still use SOF_IPC_MSG_MAX_SIZE. For future platforms, there will
be a new fw_ready function and the platform-specific allocation
will take place there.

Signed-off-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Bard Liao <bard.liao@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Message-Id: <20211008093836.28210-1-peter.ujfalusi@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>