scsi: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required

For the basic SCSI infrastructure files that are exporting symbols
but not modules themselves, add in the basic export.h header file
to allow the exports.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/scsi/scsi_tgt_if.c b/drivers/scsi/scsi_tgt_if.c
index 0172de1..6209110 100644
--- a/drivers/scsi/scsi_tgt_if.c
+++ b/drivers/scsi/scsi_tgt_if.c
@@ -22,6 +22,7 @@
 #include <linux/miscdevice.h>
 #include <linux/gfp.h>
 #include <linux/file.h>
+#include <linux/export.h>
 #include <net/tcp.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>