pci: Fix files needing export.h for EXPORT_SYMBOL/THIS_MODULE

They were implicitly getting it from device.h --> module.h but
we want to clean that up.  So add the minimal header for these
macros.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/pci/hotplug/pcihp_slot.c b/drivers/pci/hotplug/pcihp_slot.c
index 3ffd9c1..8c05a18 100644
--- a/drivers/pci/hotplug/pcihp_slot.c
+++ b/drivers/pci/hotplug/pcihp_slot.c
@@ -24,6 +24,7 @@
  */
 
 #include <linux/pci.h>
+#include <linux/export.h>
 #include <linux/pci_hotplug.h>
 
 static struct hpp_type0 pci_default_type0 = {