bridge: update max_gso_segs and max_gso_size

It can be useful to lower max_gso_segs on NIC with very low
number of TX descriptors like bcmgenet.

However, this is defeated by bridge since it does not propagate
the lower value of max_gso_segs and max_gso_size.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Petri Gynther <pgynther@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>