Revert "veth: Add updating of trans_start"

This reverts commit e66e257a. The veth
driver no longer needs these hacks which are slightly detrimential to
the fast path performance, because the bonding driver is keeping track
of TX times of ARP and NS probes by itself, which it should.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>