siena: only report generic filters in get_ts_info

CC: Solarflare linux maintainers <linux-net-drivers@solarflare.com>
CC: Shradha Shah <sshah@solarflare.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>