r8169: initialize rtl8169_stats seqlock

Boris reports he's seeing:
> [    9.195943] INFO: trying to register non-static key.
> [    9.196031] the code is fine but needs lockdep annotation.
> [    9.196031] turning off the locking correctness validator.
> [    9.196031] CPU: 1 PID: 933 Comm: modprobe Not tainted 3.14.0-rc4+ #1
with the r8169 driver.

These are occuring because the seqcount embedded in u64_stats_sync on
32-bit SMP is uninitialized which is making lockdep unhappy.

Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>