dm: scsi: Split out the bus scanning code

Split out the code that scans a single SCSI bus into a separate function.
This will allow it to be used from driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/scsi.h

@@ -219,6 +219,14 @@ int scsi_bus_reset(struct udevice *dev);
  */
 int scsi_scan(bool verbose);
 
+/**
+ * scsi_scan_dev() - scan a SCSI bus and create devices
+ *
+ * @dev:	SCSI bus
+ * @verbose:	true to show information about each device found
+ */
+int scsi_scan_dev(struct udevice *dev, bool verbose);
+
 #ifndef CONFIG_DM_SCSI
 void scsi_low_level_init(int busdevfunc);
 void scsi_init(void);