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/libsas/sas_task.c b/drivers/scsi/libsas/sas_task.c
index b13a334..a78e5bd 100644
--- a/drivers/scsi/libsas/sas_task.c
+++ b/drivers/scsi/libsas/sas_task.c
@@ -1,4 +1,5 @@
 #include <linux/kernel.h>
+#include <linux/export.h>
 #include <scsi/sas.h>
 #include <scsi/libsas.h>