wifi: ath11k: move firmware stats out of debugfs

Currently, firmware stats, comprising pdev, vdev and beacon stats are
part of debugfs. In firmware pdev stats, firmware reports the final
Tx power used to transmit each packet. If driver wants to know the
final Tx power being used at firmware level, it can leverage from
firmware pdev stats.

Move firmware stats out of debugfs context in order to leverage
the final Tx power reported in it even when debugfs is disabled.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-01100-QCAHKSWPL_SILICONZ-1
Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.5.0.1-01100-QCAHKSWPL_SILICONZ-1
Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220603082814.31466-2-quic_adisi@quicinc.com