ipvlan: Fix 64-bit statistics seqcount initialization

On 32-bit hosts and with CONFIG_DEBUG_LOCK_ALLOC we should be seeing a
lockdep splat indicating this seqcount is not correctly initialized, fix
that by using the proper helper function: netdev_alloc_pcpu_stats().

Fixes: 2ad7bf36

 ("ipvlan: Initial check-in of the IPVLAN driver.")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>