wifi: ath12k: remove MHI LOOPBACK channels

There is no driver to match these two channels, so
remove them. This fixes warnings from MHI subsystem during suspend:

mhi mhi0_LOOPBACK: 1: Failed to reset channel, still resetting
mhi mhi0_LOOPBACK: 0: Failed to reset channel, still resetting

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4
Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240412060620.27519-3-quic_bqiang@quicinc.com