wifi: ath12k: do not restore ASPM in case of single MSI vector

Current code enables ASPM by default, it allows MHI to enter M2 state.
In case of one MSI vector, system hang is observed if ath12k does MHI
register reading in this state.

The workaround here is to prevent MHI from entering M2 state, this can
be done by disabling ASPM if only one MSI vector is used. When using 32
vectors ASPM is enabled as before.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4
Signed-off-by: Kang Yang <quic_kangyang@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20231121021304.12966-7-quic_kangyang@quicinc.com

drivers/net/wireless/ath/ath12k/pci.c

@@ -1094,7 +1094,10 @@ int ath12k_pci_start(struct ath12k_base *ab)
 
 	set_bit(ATH12K_PCI_FLAG_INIT_DONE, &ab_pci->flags);
 
+	if (test_bit(ATH12K_PCI_FLAG_MULTI_MSI_VECTORS, &ab_pci->flags))
 		ath12k_pci_aspm_restore(ab_pci);
+	else
+		ath12k_info(ab, "leaving PCI ASPM disabled to avoid MHI M2 problems\n");
 
 	ath12k_pci_ce_irqs_enable(ab);
 	ath12k_ce_rx_post_buf(ab);