Fixes the following sparse warning:
drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c:172:1: warning:
symbol 'stm32_dwmac_pm_ops' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>