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: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

stm324xx family chips support Synopsys MAC 3.510 IP.
This patch adds settings for logical glue logic:
-clocks
-mode selection MII or RMII.
Reviewed-by: NJoachim Eastwood <manabian@gmail.com>
Acked-by: NGiuseppe Cavallaro <peppe.cavallaro@st.com>
Tested-by: NMaxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: NAlexandre TORGUE <alexandre.torgue@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>