drivers/video/bw2.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/bw2.c

@@ -319,8 +319,10 @@ static int __devinit bw2_probe(struct platform_device *op)
 
 	info->screen_base = of_ioremap(&op->resource[0], 0,
 				       info->fix.smem_len, "bw2 ram");
-	if (!info->screen_base)
+	if (!info->screen_base) {
+		err = -ENOMEM;
 		goto out_unmap_regs;
+	}
 
 	bw2_blank(FB_BLANK_UNBLANK, info);