video: fbdev: cobalt_lcdfb: Handle return NULL error from devm_ioremap

Here, If devm_ioremap will fail. It will return NULL.
Kernel can run into a NULL-pointer dereference.
This error check will avoid NULL pointer dereference.

Signed-off-by: Arvind Yadav <[e-mail]>
Acked-by: Yoichi Yuasa <[e-mail]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>

drivers/video/fbdev/cobalt_lcdfb.c

···
 	info->screen_size = resource_size(res);
 	info->screen_base = devm_ioremap(&dev->dev, res->start,
 					 info->screen_size);
+	if (!info->screen_base) {
+		framebuffer_release(info);
+		return -ENOMEM;
+	}
+
 	info->fbops = &cobalt_lcd_fbops;
 	info->fix = cobalt_lcdfb_fix;
 	info->fix.smem_start = res->start;