arm64: dts: rockchip: remove keep-power-in-suspend from sdhci of rk3399-sapphire

sdhci for rk3399-sapphire works for eMMC but keep-power-in-suspend
is an optional property for SDIO.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-sapphire.dtsi

@@ -541,7 +541,6 @@ &saradc {
 
 &sdhci {
 	bus-width = <8>;
-	keep-power-in-suspend;
 	mmc-hs400-1_8v;
 	mmc-hs400-enhanced-strobe;
 	non-removable;