net/core: make function ___gnet_stats_copy_basic() static

Fixes the following sparse warning:

net/core/gen_stats.c:166:1: warning:
 symbol '___gnet_stats_copy_basic' was not declared. Should it be static?

Fixes: 5e111210 ("net/core: Add new basic hardware counter")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Acked-by: NEelco Chaudron <echaudro@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/gen_stats.c

@@ -162,7 +162,7 @@ __gnet_stats_copy_basic(const seqcount_t *running,
 }
 EXPORT_SYMBOL(__gnet_stats_copy_basic);
 
-int
+static int
 ___gnet_stats_copy_basic(const seqcount_t *running,
 			 struct gnet_dump *d,
 			 struct gnet_stats_basic_cpu __percpu *cpu,