wifi: ath12k: Add htt_stats_dump file ops support

Add dump_htt_stats file operation to dump the stats value requested
for the requested stats_type.
Stats sent from firmware will be cumulative. Hence add debugfs to reset
the requested stats type.

Example with one ath12k device:

ath12k
`-- pci-0000:06:00.0
    |-- mac0
        `-- htt_stats
        |-- htt_stats_type
        |-- htt_stats_reset

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-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: Dinesh Karthikeyan <quic_dinek@quicinc.com>
Co-developed-by: Ramya Gnanasekar <quic_rgnanase@quicinc.com>
Signed-off-by: Ramya Gnanasekar <quic_rgnanase@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20240626085854.2500681-3-quic_rgnanase@quicinc.com