riscv: dts: sifive: fu540-c000: align dma node name with dtschema

Fixes dtbs_check warnings like:

  dma@3000000: $nodename:0: 'dma@3000000' does not match '^dma-controller(@.*)?$'
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20220407193856.18223-1-krzysztof.kozlowski@linaro.org
Fixes: c5ab54e9 ("riscv: dts: add support for PDMA device of HiFive Unleashed Rev A00")
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/boot/dts/sifive/fu540-c000.dtsi

@@ -167,7 +167,7 @@ uart0: serial@10010000 {
 			clocks = <&prci FU540_PRCI_CLK_TLCLK>;
 			status = "disabled";
 		};
-		dma: dma@3000000 {
+		dma: dma-controller@3000000 {
 			compatible = "sifive,fu540-c000-pdma";
 			reg = <0x0 0x3000000 0x0 0x8000>;
 			interrupt-parent = <&plic0>;