PCI: Move jailhouse's isolated function handling to pci_scan_slot()

PCI: Move jailhouse's isolated function handling to pci_scan_slot()

The special case of the jailhouse hypervisor passing through individual PCI
functions handles scanning for PCI functions even if function 0 does not
exist. Previously this was done with an extra loop duplicating the one in
pci_scan_slot(). By incorporating the check for jailhouse_paravirt() into
pci_scan_slot() we can instead do this as part of the normal slot scan.
Note that with the assignment of dev->multifunction gated by fn > 0 we set
dev->multifunction unconditionally for all functions if function 0 is
missing just as in the existing jailhouse loop.

The only functional change is that we now call pcie_aspm_init_link_state()
for these functions, but this already happened if function 0 was passed
through and should not be a problem.

Link: https://lore.kernel.org/linux-pci/20220408224514.GA353445@bhelgaas/
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20220628143100.3228092-4-schnelle@linux.ibm.com
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>