net: fec: fix initial runtime PM refcount

The clocks are initially active and thus the device is marked active.
This still keeps the PM refcount at 0, the pm_runtime_put_autosuspend()
call at the end of probe then leaves us with an invalid refcount of -1,
which in turn leads to the device staying in suspended state even though
netdev open had been called.

Fix this by initializing the refcount to be coherent with the initial
device status.

Fixes:
8fff755e

 (net: fec: Ensure clocks are enabled while using mdio bus)

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>