ARM: dts: mmp2-olpc-xo-1-75: clear the warnings when make dtbs

The check_spi_bus_bridge() in scripts/dtc/checks.c requires that the node
have "spi-slave" property must with "#address-cells = <0>" and
"#size-cells = <0>". But currently both "#address-cells" and "#size-cells"
properties are deleted, the corresponding default values are 2 and 1. As a
result, the check fails and below warnings is displayed.

arch/arm/boot/dts/mmp2.dtsi:472.23-480.6: Warning (spi_bus_bridge): \
/soc/apb@d4000000/spi@d4037000: incorrect #address-cells for SPI bus
  also defined at arch/arm/boot/dts/mmp2-olpc-xo-1-75.dts:225.7-237.3
arch/arm/boot/dts/mmp2.dtsi:472.23-480.6: Warning (spi_bus_bridge): \
/soc/apb@d4000000/spi@d4037000: incorrect #size-cells for SPI bus
  also defined at arch/arm/boot/dts/mmp2-olpc-xo-1-75.dts:225.7-237.3
arch/arm/boot/dts/mmp2-olpc-xo-1-75.dtb: Warning (spi_bus_reg): \
Failed prerequisite 'spi_bus_bridge'

Because the value of "#size-cells" is already defined as zero in the node
"ssp3: spi@d4037000" in arch/arm/boot/dts/mmp2.dtsi. So we only need to
explicitly add "#address-cells = <0>" and keep "#size-cells" no change.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20201207084752.1665-2-thunder.leizhen@huawei.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/mmp2-olpc-xo-1-75.dts

@@ -223,8 +223,7 @@ accelerometer@1d {
 };
 
 &ssp3 {
-	/delete-property/ #address-cells;
-	/delete-property/ #size-cells;
+	#address-cells = <0>;
 	spi-slave;
 	status = "okay";
 	ready-gpios = <&gpio 125 GPIO_ACTIVE_HIGH>;