The lion gmac node currently uses opposite active-values for the
gmac phy reset pin. The gpio-declaration uses active-high while the
separate snps,reset-active-low property marks the pin as active low.

While on the kernel side this works ok, other DT users may get
confused - as seen with uboot right now.

So bring this in line and make both properties match, similar to the
other Rockchip board.

Fixes: d99a02bc ("arm64: dts: rockchip: add RK3368-uQ7 (Lion) SoM")
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20200607212909.920575-1-heiko@sntech.de