fb: handle NULL pointers in framebuffer release

This function is called with a potential NULL pointer in
picolcd_init_framebuffer() and it causes a static checker warning.  This
used to handle NULL pointers when the picolcd code was written, but a
couple months later we added the "info->apertures" dereference.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/fbsysfs.c

@@ -80,6 +80,8 @@ EXPORT_SYMBOL(framebuffer_alloc);
  */
 void framebuffer_release(struct fb_info *info)
 {
+	if (!info)
+		return;
 	kfree(info->apertures);
 	kfree(info);
 }