netinet/tcp.h: add tcp zerocopy related changes from linux v5.11

see

  linux commit 18fb76ed53865c1b5d5f0157b1b825704590beb5
  net-zerocopy: Copy straggler unaligned data for TCP Rx. zerocopy.

  linux commit 94ab9eb9b234ddf23af04a4bc7e8db68e67b8778
  net-zerocopy: Defer vm zap unless actually needed.
1 file changed