x86/jailhouse: Enable PCI mmconfig access in inmates

Use the PCI mmconfig base address exported by jailhouse in boot parameters
in order to access the memory mapped PCI configuration space.

[Jan: rebased, fixed !CONFIG_PCI_MMCONFIG, used pcibios_last_bus]

Signed-off-by: Otavio Pontes <otavio.pontes@intel.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: jailhouse-dev@googlegroups.com
Cc: linux-pci@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lkml.kernel.org/r/2ee9e4401fa22377b3965893a558120f169be82b.1520408357.git.jan.kiszka@siemens.com

diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
index 0b40482..7389db5 100644
--- a/arch/x86/pci/mmconfig-shared.c
+++ b/arch/x86/pci/mmconfig-shared.c
@@ -94,8 +94,8 @@ static struct pci_mmcfg_region *pci_mmconfig_alloc(int segment, int start,
 	return new;
 }
 
-static struct pci_mmcfg_region *__init pci_mmconfig_add(int segment, int start,
-							int end, u64 addr)
+struct pci_mmcfg_region *__init pci_mmconfig_add(int segment, int start,
+						 int end, u64 addr)
 {
 	struct pci_mmcfg_region *new;