wifi: ath12k: add get_txpower mac ops

wifi: ath12k: add get_txpower mac ops

Driver does not support get_txpower mac ops because of which
cfg80211 returns vif->bss_conf.txpower to user space. bss_conf.txpower
gets its value from ieee80211_channel->max_reg_power. However, the final
txpower is dependent on few other parameters apart from max regulatory
supported power. It is the firmware which knows about all these
parameters and considers the minimum for each packet transmission.

All ath12k firmware reports the final TX power in firmware pdev stats
which falls under fw_stats. add get_txpower mac ops to get the TX power
from firmware leveraging fw_stats and return it accordingly.

While at it, there is a possibility that repeated stats request WMI
commands are queued to FW if mac80211/userspace does get tx power back
to back(in Multiple BSS cases). This could potentially consume the WMI
queue completely. Hence limit this by fetching the power only for every
5 seconds and reusing the value until the refresh timeout or when there
is a change in channel.

Also remove init_completion(&ar->fw_stats_complete) in
ath12k_mac_hw_register() as ath12k_fw_stats_init() takes care of
it for each ar.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Aditya Kumar Singh <aditya.kumar.singh@oss.qualcomm.com>
Signed-off-by: Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>
Reviewed-by: Mahendran P <quic_mahep@quicinc.com>
Link: https://patch.msgid.link/20250306102215.1300522-3-rameshkumar.sundaram@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>