video: fbdev: imxfb: fix a typo in imxfb_probe()

Fix the return value check which testing the wrong variable
in imxfb_probe().

b.zolnierkie: please note that ->screen_base and ->screen_buffer
are equivalent (they are part of unnamed union in struct fb_info)

Fixes: 739a643 ("video: fbdev: imxfb: fix sparse warnings about using incorrect types")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/imxfb.c

@@ -976,7 +976,7 @@ static int imxfb_probe(struct platform_device *pdev)
 	fbi->map_size = PAGE_ALIGN(info->fix.smem_len);
 	info->screen_buffer = dma_alloc_wc(&pdev->dev, fbi->map_size,
 					   &fbi->map_dma, GFP_KERNEL);
-	if (!info->screen_base) {
+	if (!info->screen_buffer) {
 		dev_err(&pdev->dev, "Failed to allocate video RAM: %d\n", ret);
 		ret = -ENOMEM;
 		goto failed_map;