This is to backport the #4886 to 201911
Calculate pool size in t1 as 24 * downlink port + 8 * uplink port
- Take both port and peer MTU into account when calculating headroom
- Worst case factor is decreased to 50%
- Mellanox-SN2700-C28D8 t0, assume 48 * 50G/5m + 8 * 100G/40m ports
- Mellanox-SN2700 (C32)
- t0: 16 * 100G/5m + 16 * 100G/40m
- t1: 16 * 100G/40m + 16 * 100G/300m
Signed-off-by: Stephen Sun <stephens@nvidia.com>