arm64: dts: hi3660: remove 'num-slots' property for dwmmc

Since 'num-slots' had already deprecated, remove the property in
device-tree file.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

arch/arm64/boot/dts/hisilicon/hi3660.dtsi

@@ -922,7 +922,6 @@ dwmmc1: dwmmc1@ff37f000 {
 			#size-cells = <0>;
 			cd-inverted;
 			compatible = "hisilicon,hi3660-dw-mshc";
-			num-slots = <1>;
 			bus-width = <0x4>;
 			disable-wp;
 			cap-sd-highspeed;
@@ -960,7 +959,6 @@ dwmmc2: dwmmc2@ff3ff000 {
 			compatible = "hisilicon,hi3660-dw-mshc";
 			reg = <0x0 0xff3ff000 0x0 0x1000>;
 			interrupts = <GIC_SPI 140 IRQ_TYPE_LEVEL_HIGH>;
-			num-slots = <1>;
 			clocks = <&crg_ctrl HI3660_CLK_GATE_SDIO0>,
 				 <&crg_ctrl HI3660_HCLK_GATE_SDIO0>;
 			clock-names = "ciu", "biu";