arm64: dts: rockchip: fix &pinctrl phy sub nodename for rk3399-orangepi

A test with the command below this error:

arch/arm64/boot/dts/rockchip/rk3399-orangepi.dt.yaml: phy:
'#phy-cells' is a required property

'phy' is a reserved nodename and should not be used for pinctrl,
so change it to 'gmac'.

make ARCH=arm64 dtbs_check
DT_SCHEMA_FILES=~/.local/lib/python3.5/site-packages/dtschema/schemas/
phy/phy-provider.yaml
Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200321215423.12176-6-jbx6244@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-orangepi.dts

@@ -554,7 +554,7 @@ pwr_btn: pwr-btn {
 		};
 	};
 
-	phy {
+	gmac {
 		phy_intb: phy-intb {
 			rockchip,pins = <3 RK_PB2 RK_FUNC_GPIO &pcfg_pull_up>;
 		};