Description of problem:
pciehp cannot detect any slot.

Version-Release number of selected component (if applicable):
4.18.0-423.el8.x86_64

How reproducible:

Steps to Reproduce:
1. Use libvirt to create a x86_64 pc-q35-6.2 VM. In grub kernel command line add pciehp.dyndbg=+p
2. boot into it
3. dmesg | grep pciehp

Actual results:
only show single related line:
```
pciehp: pcie_port_service_register = 0
```

Expected results:
It should show lines like following:
```
[ 1.360623] pciehp: pcie_port_service_register = 0
[ 1.362499] pcieport 0000:00:02.0: pciehp: Slot Capabilities : 0x0002007b
[ 1.362508] pcieport 0000:00:02.0: pciehp: Slot Status : 0x0050
[ 1.362517] pcieport 0000:00:02.0: pciehp: Slot Control : 0x01c0
[ 1.362533] pcieport 0000:00:02.0: pciehp: Slot #0 AttnBtn+ PwrCtrl+ MRL- AttnInd+ PwrInd+ HotPlug+ Surprise+ Interlock+ NoCompl- IbPresDis- LLActRep+
```

Additional info:
The PCIe hotplug is broken. When plug in new devices, the pcie cannot trigger the hot-plug action. It does not show `Attention button pressed`, `Link Up`, etc.