net: stmmac: fix failed to suspend if phy based WOL is enabled

With the latest net-next tree, if test suspend/resume after enabling
WOL, we get error as below:

[  487.086365] dpm_run_callback(): mdio_bus_suspend+0x0/0x30 returns -16
[  487.086375] PM: Device stmmac-0:00 failed to suspend: error -16

-16 means -EBUSY, this is because I didn't enable wakeup of the correct
device when implementing phy based WOL feature. To be honest, I caught
the issue when implementing phy based WOL and then fix it locally, but
forgot to amend the phy based wol patch. Today, I found the issue by
testing net-next tree.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>