r8169: Fix sleeping function called during get_stats64, v2

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=104031
Fixes: 6e85d5ad

Based on the discussion starting at
http://www.spinics.net/lists/netdev/msg342193.html



Tested locally on RTL8168evl/8111evl with various concurrent processes
accessing /proc/net/dev while changing the link state as well as
removing/reloading the r8169 module.

Signed-off-by: Corinna Vinschen <vinschen@redhat.com>
Tested-by: poma <pomidorabelisima@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>