fbdev: stifb: Fix info entry in sti_struct on error path

Minor fix to reset the info field to NULL in case of error.
Signed-off-by: Helge Deller <deller@gmx.de>

drivers/video/fbdev/stifb.c

@@ -1413,6 +1413,7 @@ static int __init stifb_init_fb(struct sti_struct *sti, int bpp_pref)
 	iounmap(info->screen_base);
 out_err0:
 	kfree(fb);
+	sti->info = NULL;
 	return -ENXIO;
 }