x86/PCI: Define to_pci_sysdata() even when !CONFIG_PCI

Recently, the to_pci_sysdata() helper was added inside the CONFIG_PCI
guard, but it is used inside a CONFIG_NUMA guard, which does not require
CONFIG_PCI.  This breaks builds on !CONFIG_PCI machines.  Make
to_pci_sysdata() available in all configurations.

Fixes: aad6aa0 ("x86/PCI: Add to_pci_sysdata() helper")
Link: https://lore.kernel.org/r/20200203215306.172000-1-Jason@zx2c4.com
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>	# build-tested

arch/x86/include/asm/pci.h

@@ -33,13 +33,13 @@ extern int pci_routeirq;
 extern int noioapicquirk;
 extern int noioapicreroute;
 
-#ifdef CONFIG_PCI
-
 static inline struct pci_sysdata *to_pci_sysdata(const struct pci_bus *bus)
 {
 	return bus->sysdata;
 }
 
+#ifdef CONFIG_PCI
+
 #ifdef CONFIG_PCI_DOMAINS
 static inline int pci_domain_nr(struct pci_bus *bus)
 {