Introduce common broadcom utility

This MR is starting point for new utility functions collection. For now only one example function is created to get noisefloor value for particular interface. Next we will add more functions based on IOCTL and/or nl vendor command and if not possible this way function to parse output of wlctrl tool in order to collect required information.

@anjancx @janusz @bartlomiej.grzeskowiak Please review.