UBI: do not print message about corruptes PEBs if we have none of them

Currently UBI prints

UBI: corrupted PEBs will be formatted

even if there are not corrupted PEBs. Fix this.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/scan.c

@@ -964,7 +964,7 @@ static int check_what_we_have(struct ubi_device *ubi, struct ubi_scan_info *si)
 		}
 	}
 
-	if (si->corr_peb_count >= 0)
+	if (si->corr_peb_count > 0)
 		ubi_msg("corrupted PEBs will be formatted");
 	return 0;
 }