wifi: ath12k: refactor ath12k_mac_register() and ath12k_mac_unregister()

wifi: ath12k: refactor ath12k_mac_register() and ath12k_mac_unregister()

Currently, the mac80211 hw registration procedure is tightly coupled with
the handling of link/radio (ar). Define a new helper function to separate
the link/radio handling from the mac80211 hw registration procedure for
improved code readability. Also, it can be easy to scale these
functionality to support single/multi link operation in the future.

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

Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20231206034920.1037449-5-quic_periyasa@quicinc.com