BTM_RegisterForVSEvents() function

* Function BTM_RegisterForVSEvents * Description This function is called to register/deregister for vendor * specific HCI events. * If is_register=TRUE, then the function will be registered; * if is_register=FALSE, then the function will be deregistered. * Returns BTM_SUCCESS if successful, * BTM_BUSY if maximum number of callbacks have already been * registered.