net: fix phy refcounting in a bunch of drivers

of_phy_find_device() increments the phy struct device refcount, which
we need to properly balance.  Add code to network drivers using this
function to ensure that the struct device refcount is correctly
balanced.

For xgene, looking back in the history, we should be able to use
of_phy_connect() with a zero flags argument for the DT case as this is
how the driver used to operate prior to de7b5b3d ("net: eth: xgene:
change APM X-Gene SoC platform ethernet to support ACPI").

This leaves the Cavium Thunder BGX unfixed; fixing this driver is a
complicated task, one which the maintainers need to be involved with.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>