The original PCIe hot-plug code required a couple of things which cause
PCI probing errors on the qemu q35 system and possibly physical systems
First, the code required the hot-plug IRQ's to be unique (i.e. not
shared). On qemu q35, all PCIe hot-plug IRQ's are identical. Fix by
allocating the IRQ as RF_SHAREABLE.
Second, the code required the Electromechanical Interlock (Slot Status
EIS) to be engaged if present (Slot Capability EIP). Several platforms
including qemu q35 set EIP but not EIS. Fix by deleting the check.