wifi: ath12k: initial debugfs support

The initial debugfs infra bringup in ath12k driver and create the ath12k debugfs
and soc-specific directories in /sys/kernel/debug/

For each ath12k device, directory will be created in <bus>-<devname>
schema under ath12k root directory.

Example with one ath12k device:
/sys/kernel/debug/ath12k/pci-0000:06:00.0

ath12k
`-- pci-0000:06:00.0
    |-- mac0

To enable ath12k debugfs support (CONFIG_ATH12K_DEBUGFS=y)

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Signed-off-by: Ramasamy Kaliappan <quic_rkaliapp@quicinc.com>
Signed-off-by: Ramya Gnanasekar <quic_rgnanase@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240320171305.655288-2-quic_rgnanase@quicinc.com