Fwk log level improvements
Created by: nicola-mazzucato-arm
Currently the FWX_LOG_ macros provide a way to print or not messages in accordance with the LOG_LEVEL chosen at build time. The strings however are voided but not removed. This PR brings some improvements in order to remove unused strings in the FWK_LOG. Some preparatory patches are required in order to accommodate for such change in the logging framework.