Function drmgr_unregister_kernel_xfer_event 

pub unsafe extern "C" fn drmgr_unregister_kernel_xfer_event(
    func: Option<unsafe extern "C" fn(drcontext: *mut c_void, info: *const dr_kernel_xfer_info_t)>,
) -> bool_

Unregister a callback function for the kernel transfer event. \return true if unregistration is successful and false if it is not (e.g., \p func was not registered).