PCI: Add missing include to drivers/pci.h

This file makes use of definitions provided in <linux/pci.h>.  This only
compiles when <linux/pci.h> is included beforehand, and creates a nasty
include dependency.  Instead, just include the correct file.
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.h

@@ -2,6 +2,8 @@
 #ifndef DRIVERS_PCI_H
 #define DRIVERS_PCI_H
 
+#include <linux/pci.h>
+
 #define PCI_FIND_CAP_TTL	48
 
 #define PCI_VSEC_ID_INTEL_TBT	0x1234	/* Thunderbolt */