Fundamentally this was wrong. Tsf is only valid
in last MPDU of a PPDU. This means tsf value was
wrong most of the time during heavy traffic.

Also I don't see much point in exposing a
redundant (and broken) tsf value. Userspace can
already read it from the dumped rx descriptor
buffer.

Cc: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>