net: stmmac: Fix WoL for PCI-based setups

WoL won't work in PCI-based setups because we are not saving the PCI EP
state before entering suspend state and not allowing D3 wake.

Fix this by using a wrapper around stmmac_{suspend/resume} which
correctly sets the PCI EP state.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>