arm64: dts: imx8mm-evk: Replace deprecated phy reset properties

Use preferred properties of phy node instead of deprecated
phy-reset-gpios (and others).  This avoids copying deprecated code into
future DTSes.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>