arm64: dts: rockchip: rk3399-firefly: remove num-slots from &sdio0 node

The option "num-slots" was deprecated long time ago, so remove it.
Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20191231191154.5587-1-jbx6244@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

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

@@ -660,7 +660,6 @@ &sdio0 {
 	keep-power-in-suspend;
 	mmc-pwrseq = <&sdio_pwrseq>;
 	non-removable;
-	num-slots = <1>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&sdio0_bus4 &sdio0_cmd &sdio0_clk>;
 	sd-uhs-sdr104;