arm64: dts: clearfog-gt-8k: 1G eth PHY reset signal

This reset signal controls the Marvell 1512 1G PHY.

Note that current implementation queries the PHY over the MDIO bus
(get_phy_device() call from of_mdiobus_register_phy()) before reset
signal deassert. If the PHY reset signal is asserted at boot time, PHY
registration fails. So current code relies on the bootloader to deassert
the reset signal.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>