video: fbdev: i740fb: use memset_io() to clear screen

sparse complains that using memset() on __iomem pointer is wrong:
incorrect type in argument 1 (different address spaces)

Use memset_io() to clear screen instead.

Tested on real i740 cards.
Signed-off-by: NOndrej Zary <linux@zary.sk>
Signed-off-by: NHelge Deller <deller@gmx.de>

drivers/video/fbdev/i740fb.c

@@ -740,7 +740,7 @@ static int i740fb_set_par(struct fb_info *info)
 	if (i)
 		return i;
 
-	memset(info->screen_base, 0, info->screen_size);
+	memset_io(info->screen_base, 0, info->screen_size);
 
 	vga_protect(par);