arm64: dts: rk3399-puma: fix gpio levels for gmac reset pin

arm64: dts: rk3399-puma: fix gpio levels for gmac reset pin

The gmac reset has opposite values for the gpio declaration
and the separate reset-active, bring this in line to make
u-boot also find the ethernet-phy.

This mimics the upstream Linux commit found on
https://lore.kernel.org/r/20200603132836.362519-1-heiko@sntech.de

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>