ARM: dts: uniphier: rename NAND node names to follow json-schema

Follow the standard nodename pattern "^nand-controller(@.*)?" defined
in Documentation/devicetree/bindings/mtd/nand-controller.yaml

Otherwise, after the dt-binding is converted to json-schema,
'make ARCH=arm dtbs_check' will show warnings like this:

nand@68000000: $nodename:0: 'nand@68000000' does not match '^nand-controller(@.*)?'

Signed-off-by: Masahiro Yamada <[e-mail]>

arch/arm/boot/dts/uniphier-ld4.dtsi

···
 			};
 		};
 
-		nand: nand@68000000 {
+		nand: nand-controller@68000000 {
 			compatible = "socionext,uniphier-denali-nand-v5a";
 			status = "disabled";
 			reg-names = "nand_data", "denali_reg";

arch/arm/boot/dts/uniphier-pro4.dtsi

···
 			};
 		};
 
-		nand: nand@68000000 {
+		nand: nand-controller@68000000 {
 			compatible = "socionext,uniphier-denali-nand-v5a";
 			status = "disabled";
 			reg-names = "nand_data", "denali_reg";

arch/arm/boot/dts/uniphier-pro5.dtsi

···
 			};
 		};
 
-		nand: nand@68000000 {
+		nand: nand-controller@68000000 {
 			compatible = "socionext,uniphier-denali-nand-v5b";
 			status = "disabled";
 			reg-names = "nand_data", "denali_reg";

arch/arm/boot/dts/uniphier-pxs2.dtsi

···
 			};
 		};
 
-		nand: nand@68000000 {
+		nand: nand-controller@68000000 {
 			compatible = "socionext,uniphier-denali-nand-v5b";
 			status = "disabled";
 			reg-names = "nand_data", "denali_reg";

arch/arm/boot/dts/uniphier-sld8.dtsi

···
 			};
 		};
 
-		nand: nand@68000000 {
+		nand: nand-controller@68000000 {
 			compatible = "socionext,uniphier-denali-nand-v5a";
 			status = "disabled";
 			reg-names = "nand_data", "denali_reg";