x86: Align x86_64 PCI_MMCONFIG with 32-bit variant

Allow to enable PCI_MMCONFIG when only SFI is present and make this option
default on. This will help consolidating both into one Kconfig statement.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: jailhouse-dev@googlegroups.com
Cc: linux-pci@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lkml.kernel.org/r/a2faf78c54f340f5549149e8b679c95950dae83d.1520408357.git.jan.kiszka@siemens.com

arch/x86/Kconfig

@@ -2658,7 +2658,8 @@ config PCI_DOMAINS
 
 config PCI_MMCONFIG
 	bool "Support mmconfig PCI config space access"
-	depends on X86_64 && PCI && ACPI
+	default y
+	depends on X86_64 && PCI && (ACPI || SFI)
 
 config PCI_CNB20LE_QUIRK
 	bool "Read CNB20LE Host Bridge Windows" if EXPERT