watchdog: fix typo in omap_wdt.c

Fix typo in omap_wdt.c introduced by a recent change
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/watchdog/omap_wdt.c

@@ -283,7 +283,7 @@ static int __init omap_wdt_probe(struct platform_device *pdev)
 	}
 
 	if (omap_wdt_dev) {
-		ret - EBUSY;
+		ret = -EBUSY;
 		goto err_busy;
 	}