Merge branch 'bpf_gso_size'

Willem de Bruijn says:

====================
See first patch for details.

Patch split across three parts { kernel feature, uapi header, tools }
following the custom for such __sk_buff changes.
====================

Acked-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>