coresight: syscfg: Add initial configfs support

coresight: syscfg: Add initial configfs support

Adds configfs subsystem and attributes to the configuration manager
to enable the listing of loaded configurations and features.

The default values of feature parameters can be accessed and altered
from these attributes to affect all installed devices using the feature.

Link: https://lore.kernel.org/r/20210723165444.1048-10-mike.leach@linaro.org
Signed-off-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210818194022.379573-10-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>