arm64: dts: agilex: align mmc node names with dtschema

The Synopsys DW MSHC bindings require node name to be 'mmc':

  dwmmc0@ff808000: $nodename:0: 'dwmmc0@ff808000' does not match '^mmc(@.*)?$'
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: NDinh Nguyen <dinguyen@kernel.org>

arch/arm64/boot/dts/intel/socfpga_agilex.dtsi

@@ -300,7 +300,7 @@
 			status = "disabled";
 		};
 
-		mmc: dwmmc0@ff808000 {
+		mmc: mmc@ff808000 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 			compatible = "altr,socfpga-dw-mshc";