net: remove unnecessary semicolon in netdev_alloc_pcpu_stats()

This semicolon causes a build error if the function call is wrapped in
parentheses.

Fixes: aabc92bb

 ("net: add __netdev_alloc_pcpu_stats() to indicate gfp flags")
Reported-by: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>