BTM_SwitchRole() function

* Function BTM_SwitchRole * Description This function is called to switch role between master and * slave. If role is already set it will do nothing. If the * command was initiated, the callback function is called upon * completion. * Returns BTM_SUCCESS if already in specified role. * BTM_CMD_STARTED if command issued to controller. * BTM_NO_RESOURCES if couldn't allocate memory to issue command * BTM_UNKNOWN_ADDR if no active link with bd addr specified * BTM_MODE_UNSUPPORTED if local device does not support role switching * BTM_BUSY if the previous command is not completed