drivers/video/mbx/mbxfb.c: correct ioremap_nocache test

The test tested not the most recently allocated value but a previously
allocated one.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/mbx/mbxfb.c

@@ -950,7 +950,7 @@ static int __devinit mbxfb_probe(struct platform_device *dev)
 
 	mfbi->fb_virt_addr = ioremap_nocache(mfbi->fb_phys_addr,
 					     res_size(mfbi->fb_req));
-	if (!mfbi->reg_virt_addr) {
+	if (!mfbi->fb_virt_addr) {
 		dev_err(&dev->dev, "failed to ioremap frame buffer\n");
 		ret = -EINVAL;
 		goto err4;