powerpc/powernv/pci: fix header guard

While looking at -Wundef warnings, the #if CONFIG_EEH stood out as a
possible candidate to convert to #ifdef CONFIG_EEH.

It seems that based on Kconfig dependencies it's not possible to build
this file without CONFIG_EEH enabled, but based on upstream discussion,
it's not clear yet that CONFIG_EEH should be enabled by default.

For now, simply fix the -Wundef warning.

Suggested-by: Nathan Chancellor <[email protected]>
Suggested-by: Joe Perches <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: ClangBuiltLinux#570
Link: https://lore.kernel.org/lkml/[email protected]/
Link: https://lore.kernel.org/lkml/CAOSf1CGoN5R0LUrU=Y=UWho1Z_9SLgCX8s3SbFJXwJXc5BYz4A@mail.gmail.com/
Link: https://lore.kernel.org/r/[email protected]

arch/powerpc/platforms/powernv/pci.c

@@ -711,7 +711,7 @@ int pnv_pci_cfg_write(struct pci_dn *pdn,
 	return PCIBIOS_SUCCESSFUL;
 }
 
-#if CONFIG_EEH
+#ifdef CONFIG_EEH
 static bool pnv_pci_cfg_check(struct pci_dn *pdn)
 {
 	struct eeh_dev *edev = NULL;