ath10k: remove unnecessary htt rx corruption check

While fixing a bug reported by Avery I went ahead
and added a warning suspecting there might be
something more to the bug. This ended up with
people reporting they see warnings during heavy
traffic. This bought me some time and helped me
understand the problem better - apparently fw/hw
can report a chained msdus as follows: 1 msdu, 1
chained, 1 msdu (0 length).

The patch removes the extra check but leaves the
other change that fixed the original skb_push
panic bug (msdu_chaining was overwritten in an
unfortunate way which made the above example to
be treated as non-chained case).

Reported-by: Yeoh Chun-Yeow <yeohchunyeow@gmail.com>
Reported-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>