ath11k: Add support for RX decapsulation offload

ath11k: Add support for RX decapsulation offload

Add support for rx decapsulation offload by advertising
the support to mac80211 during registration. Also ensure
the frames have the RX_FLAG_8023 flag set in decap offload
frames before passing to mac80211.

Since the packets delivered to the driver are in 802.3 format, these
can be sent to the network core with minimal processing in mac80211.
This helps in releasing some CPU cycles in the host processor and
thereby improving the performance.

Two exceptions are made before passing decap frames, one is
for EAPOL packets since mac80211 8023 fast rx for the sta
is set only after authorization, other case is for multicast
packets to validate PN in mac80211. In both the cases the
decap frames are converted to 80211 frame and sent to mac80211.

Ethernet decap can be enabled by using frame_mode modparam:

insmod ath11k frame_mode=2

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-00844-QCAHKSWPL_SILICONZ-1 v2

Co-developed-by: Manikanta Pubbisetty <mpubbise@codeaurora.org>
Signed-off-by: Manikanta Pubbisetty <mpubbise@codeaurora.org>
Signed-off-by: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210721204217.120572-1-jouni@codeaurora.org