video: fbdev: imxfb: fix sparse warnings about using incorrect types

Use ->screen_buffer instead of ->screen_base to fix sparse warnings.

[ Please see commit 17a7b0b ("fb.h: Provide alternate screen_base
  pointer") for details. ]

Reported-by: kbuild test robot <lkp@intel.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/imxfb.c

@@ -974,9 +974,8 @@ static int imxfb_probe(struct platform_device *pdev)
 	}
 
 	fbi->map_size = PAGE_ALIGN(info->fix.smem_len);
-	info->screen_base = dma_alloc_wc(&pdev->dev, fbi->map_size,
-					 &fbi->map_dma, GFP_KERNEL);
-
+	info->screen_buffer = dma_alloc_wc(&pdev->dev, fbi->map_size,
+					   &fbi->map_dma, GFP_KERNEL);
 	if (!info->screen_base) {
 		dev_err(&pdev->dev, "Failed to allocate video RAM: %d\n", ret);
 		ret = -ENOMEM;
@@ -1046,7 +1045,7 @@ static int imxfb_probe(struct platform_device *pdev)
 	if (pdata && pdata->exit)
 		pdata->exit(fbi->pdev);
 failed_platform_init:
-	dma_free_wc(&pdev->dev, fbi->map_size, info->screen_base,
+	dma_free_wc(&pdev->dev, fbi->map_size, info->screen_buffer,
 		    fbi->map_dma);
 failed_map:
 	iounmap(fbi->regs);
@@ -1077,7 +1076,7 @@ static int imxfb_remove(struct platform_device *pdev)
 	pdata = dev_get_platdata(&pdev->dev);
 	if (pdata && pdata->exit)
 		pdata->exit(fbi->pdev);
-	dma_free_wc(&pdev->dev, fbi->map_size, info->screen_base,
+	dma_free_wc(&pdev->dev, fbi->map_size, info->screen_buffer,
 		    fbi->map_dma);
 	iounmap(fbi->regs);
 	release_mem_region(res->start, resource_size(res));