gso: do not gro on small packets

gso: do not gro on small packets

This has two benefits: fix an issue where small packets can be
padded to 64 bytes by the ethernet layer, and we included these bytes
in the tcp stream; and also if we receive a small packet, it signals
that this tcp stream is likely more latency-sensitive than throughput-
sensitive, and skipping gro buffering should be beneficial.

Type: fix
Change-Id: I165b97673d8cdce95ebf0a66c362ae9f9e6f3f34
Signed-off-by: Aloys Augustin <aloaugus@cisco.com>