ath10k: report A-MSDU subframes individually

HW reports each A-MSDU subframe as a separate
sk_buff. It is impossible to configure it to
behave differently.

Until now ath10k was reconstructing A-MSDUs from
subframes which involved a lot of memory
operations. This proved to be a significant
contributor to degraded RX performance.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: document decap modes

Clarify how each decap mode works in one place.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: cleanup RX decap handling

Simplify decapping code and make it easier to
understand.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: fix Native Wifi decap mode RX

NWifi decap mode always reports 802.11 Data
Frames, even when QoS Data Frames are actually
received.

This made mac80211 not report frame priority
properly (since there was no QoS Control field).

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: align RX frames properly

Ethernet-like decapping mode leaves IP protocol
frame not aligned to 4-byte boundaries. This leads
to re-aligning in mac80211 which in turn leads to
poor CPU cache behaviour on some machines.

Since HW doesn't allow to change payload offset
properly the solution is to force HW to decap in
Native Wifi mode which always has 24-bytes long
802.11 header (even for QoS frames). This means IP
frame is properly aligned in this decap mode.

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