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: Wei Yongjun <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
 		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;