ath11k: enable PN offload

Enabling PN checking in the hardware; hardware checks
the PN of the received packets and reports the errors
to the host for further handling; default action is to
drop such packets. TSC (TKIP sequence counter)
validation is also offloaded.

Hardware validates PN/TSC only for unicast packets;
for group addressed packets, PN validation is done
in mac80211.

PN errors are reported to the driver via WBM RX release
ring and can be dumped by using the following command.

"cat /sys/kernel/debug/ath11k/soc_rx_stats | grep -i pn"

Sample Output:
PN check fail: 210

Signed-off-by: Manikanta Pubbisetty <mpubbise@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>