ASoC: SOF: pci: change the default firmware path when the community key is used

ASoC: SOF: pci: change the default firmware path when the community key is used

Since ApolloLake, Intel platforms require signed firmware. On all
Windows platforms the default is to require the Intel production key
be used. But some platforms allow for a community key to be used,
which allows developers to compile/build their own firmware.

In the linux-firmware tree, the default intel/sof path is used for
firmwares signed for the production key, and files signed with the
community key are located in intel/sof/community.

Since we don't have an API to query which key is used on what
platforms, we have to rely on DMI-based quirks.

Developers can bypass this mechanism by setting a kernel 'fw_path'
module parameter. Additional dynamic debug traces are provided to help
debug cases where the wrong file might be used.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200107160840.1524-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>