PCI: Extend isolated function probing to LoongArch

PCI: Extend isolated function probing to LoongArch

commit a02fd05661d73a8507dd70dd820e9b984490c545 upstream.

Like s390 and the jailhouse hypervisor, LoongArch's PCI architecture allows
passing isolated PCI functions to a guest OS instance. So it is possible
that there is a multi-function device without function 0 for the host or
guest.

Allow probing such functions by adding a IS_ENABLED(CONFIG_LOONGARCH) case
in the hypervisor_isolated_pci_functions() helper.

This is similar to commit 189c6c33ff42 ("PCI: Extend isolated function
probing to s390").

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20250624062927.4037734-1-chenhuacai@loongson.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>