drivers/video/arcfb.c: fix error return code

Convert a nonnegative error return code to a negative one, as returned
elsewhere in the function.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}
// </smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/arcfb.c

@@ -552,6 +552,7 @@ static int __devinit arcfb_probe(struct platform_device *dev)
 				"arcfb", info)) {
 			printk(KERN_INFO
 				"arcfb: Failed req IRQ %d\n", par->irq);
+			retval = -EBUSY;
 			goto err1;
 		}
 	}