PCI: Fix missing prototype for pcie_port_acpi_setup()

This fixes a "no previous prototype" warning for pcie_port_acpi_setup()
found via "make W=1".

[bhelgaas: changelog]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/portdrv_acpi.c

@@ -17,6 +17,7 @@
 
 #include "aer/aerdrv.h"
 #include "../pci.h"
+#include "portdrv.h"
 
 /**
  * pcie_port_acpi_setup - Request the BIOS to release control of PCIe services.