scsi_scan.c: quiet sparse noise

scsi_scan.c: quiet sparse noise

Include the <scsi/scsi_scan.h> header to pick up the extern prototype of scsi_complete_async_scans in order to quiet the following sparse warning:

warning: symbol 'scsi_complete_async_scans' was not declared. Should it be static?

---

index 012f73a..6e3ca0a 100644
@@ -42,6 +42,7 @@
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_transport.h>
 #include <scsi/scsi_eh.h>
+#include <scsi/scsi_scan.h>
 
 #include "scsi_priv.h"
 #include "scsi_logging.h"