scsi: Change scsi_scan() to be able to return value

With DM_SCSI this function will return more than one return value to
cover errors.

Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/scsi.c b/common/scsi.c
index ba65616..839b30b 100644
--- a/common/scsi.c
+++ b/common/scsi.c
@@ -524,7 +524,7 @@
  * (re)-scan the scsi bus and reports scsi device info
  * to the user if mode = 1
  */
-void scsi_scan(int mode)
+int scsi_scan(int mode)
 {
 	unsigned char i, lun;
 	int ret;
@@ -558,6 +558,7 @@
 #ifndef CONFIG_SPL_BUILD
 	setenv_ulong("scsidevs", scsi_max_devs);
 #endif
+	return 0;
 }
 
 #ifdef CONFIG_BLK