[SCSI] cleanup usages of scsi_complete_async_scans

Now that scsi registers its async scan work with the async subsystem,
wait_for_device_probe() is sufficient for ensuring all scanning is
complete.

[jejb: fix merge problems with eea03c20ae Make wait_for_device_probe() also do scsi_complete_async_scans()]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

include/scsi/scsi_scan.h

@@ -1,11 +0,0 @@
-#ifndef _SCSI_SCSI_SCAN_H
-#define _SCSI_SCSI_SCAN_H
-
-#ifdef CONFIG_SCSI
-/* drivers/scsi/scsi_scan.c */
-extern int scsi_complete_async_scans(void);
-#else
-static inline int scsi_complete_async_scans(void) { return 0; }
-#endif
-
-#endif /* _SCSI_SCSI_SCAN_H */