ASoC: SOF: Add path definition for external firmware libraries

IPC4 based firmware supports dynamically loaded external libraries.
The libraries will be not stored alongside of the firmware or tplg files.

For intel platforms the default path will be:
intel/avs-lib|sof-ipc4-lib/<platform>/ if a community key is used on the
given machine then the libraries will be under 'community' directory, like
it is done for the firmware itself.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Chao Song <chao.song@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20221020121238.18339-12-peter.ujfalusi@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>