wifi: ath12k: Modify add and remove chanctx ops for single wiphy support

Modify add and remove chanctx mac80211 ops to fetch the correct
radio(ar) based on channel context.

This change also introduces new helper function to fetch the
radio/ar based on channel context and ieee80211_chan which internally
uses the radio's low/high freq range.

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: Sriram R <quic_srirrama@quicinc.com>
Signed-off-by: Rameshkumar Sundaram <quic_ramess@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240405194519.1337906-3-quic_ramess@quicinc.com