arm: mvebu: turris_omnia: Fix ethernet PHY reset gpio FDT fixup

arm: mvebu: turris_omnia: Fix ethernet PHY reset gpio FDT fixup

For board revisions where the WAN ethernet PHY reset GPIO is controllable
via MCU we currently insert a phy-reset-gpios property into the ethernet
controller node. The mvneta driver parses this property and uses the
GPIO to reset the PHY.

But this phy-reset-gpios property is not a valid DT binding in upstream
kernel. Instead, a reset-gpios property should be inserted into the
ethernet PHY node. This correct DT binding is supported by the DM ETH PHY
U-Boot driver.

Insert the reset-gpios property into the WAN PHY node instead the
phy-reset-gpios property in WAN ETH node so that Linux will correctly use
the reset GPIO.

Enable the CONFIG_DM_ETH_PHY config option so that U-Boot will also use
the correct DT property.

Note: currently there are 4 ethernet controller drivers parsing the
wrong DT property: dwc_eth_qos, fex_mxc, mvneta and mvpp2. We should
convert all relevant device-trees to use reset-gpios so that we can get
rid of these drivers parsing this property.

Fixes: 1da53ae26afc ("arm: mvebu: turris_omnia: Add support for design with SW reset signals")
Signed-off-by: Marek Behún <kabel@kernel.org>