net: hns: make function hns_gmac_wait_fifo_clean() static

Fixes the following sparse warning:

drivers/net/ethernet/hisilicon/hns/hns_dsaf_gmac.c:322:5: warning:
 symbol 'hns_gmac_wait_fifo_clean' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns/hns_dsaf_gmac.c

@@ -319,7 +319,7 @@ static void hns_gmac_set_promisc(void *mac_drv, u8 en)
 		hns_gmac_set_uc_match(mac_drv, en);
 }
 
-int hns_gmac_wait_fifo_clean(void *mac_drv)
+static int hns_gmac_wait_fifo_clean(void *mac_drv)
 {
 	struct mac_driver *drv = (struct mac_driver *)mac_drv;
 	int wait_cnt;