Calling two copy_to_user() for very small regions has very high overhead.

Switch to inlined unsafe_put_user() to save one stac/clac sequence,
and avoid copy_to_user().
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: NSoheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>