wifi: ath12k: Add helper function ath12k_mac_update_freq_range()

wifi: ath12k: Add helper function ath12k_mac_update_freq_range()

In a subsequent change, the frequency range needs to be updated with
each regulatory update. Since the current function also modifies the
DISABLED flag in the actual channel list, which should always align
with hardware-supported start and end frequencies rather than the
current operating ones, the existing function cannot be called again.
Therefore, the logic for setting the frequency range needs to be
refactored.

To address this, refactor the frequency setting part into a new
helper function, ath12k_mac_update_freq_range(). Since this needs
to be done independently of updating the DISABLED flag, call the new
helper function ath12k_mac_update_freq_range() after updating the
channel list for each band.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-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: Rajat Soni <quic_rajson@quicinc.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250408042128.720263-2-quic_rajson@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>