Merge branch 'tcp-redundant-checks'

Soheil Hassas Yeganeh says:

====================
tcp: simplify ack tx timestamps

v2:
- Fully remove SKBTX_ACK_TSTAMP, as suggested by Willem de Bruijn.

This patch series aims at removing redundant checks and fields
for ack timestamps for TCP.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>