ath11k: change to use dynamic memory for channel list of scan

Currently there are about 60 channels for 6 GHz, then the size of
chan_list in struct scan_req_params which is 40 is not enough to
fill all the channel list of 6 GHz.

Use dynamic memory to save the channel list of scan.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Signed-off-by: Wen Gong <quic_wgong@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20211129110939.15711-1-quic_wgong@quicinc.com