net: qcom/emac: grab a reference to the phydev on ACPI systems

Commit 6ffe1c4c ("net: qcom/emac: fix of_node and phydev leaks")
fixed the problem with reference leaks on phydev, but the fix is
device-tree specific.  When the driver unloads, the reference is
dropped only on DT systems.

Instead, it's cleaner if up grab an reference on ACPI systems.
When the driver unloads, we can drop the reference without having
to check whether we're on a DT system.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>