ARM: dts: imx7d-pico: Pass the Ethernet PHY reset GPIO

Pass the "phy-reset-gpios" property in order to describe the GPIO
that performs the Ethernet PHY reset.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>