wifi: ath12k: refactor ath12k_mac_setup_channels_rates()

Currently, the MAC setup helper function is accessing the mac80211 hw
data. In the future, to support single/multi link operation, need to
decouple the mac80211 hw data from this helper function so that it can be
easy to scale these functions to support single/multi link operations. So
remove the mac80211 hw access from the ath12k_mac_setup_channels_rates()
helper function.

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/20231206034920.1037449-4-quic_periyasa@quicinc.com