Remove Broadcom copyrights

[emilf]

Broadcom doesn't allow the WICED source to be published. However, the platform configurations and patches are probably fair use (for patches) or non-copyrightable due to being configuration [1]

Removing the copyright notices is mostly to prevent any bots they might have from flagging the repo. I doubt Broadcom minds this project, since while all versions of WICED on Github were DMCAd at one point, this project was left alone.