arm64: dts: qcom: sm8750: add memory node for adsp fastrpc

Add optional memory heap node that can be used for ADSP fastrpc.

Cc: Ekansh Gupta <quic_ekangupt@quicinc.com>
Cc: Srinivas Kandagatla <srini@kernel.org>
Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
Link: https://lore.kernel.org/r/20251209-sm8750-fastrpc-adsp-v3-1-ccfff49a8af9@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: laklimov

arch/arm64/boot/dts/qcom/sm8750.dtsi

@@ -540,6 +540,14 @@
 			reg = <0x0 0xff800000 0x0 0x800000>;
 			no-map;
 		};
+
+		adsp_rpc_remote_heap_mem: adsp-rpc-remote-heap {
+			compatible = "shared-dma-pool";
+			alloc-ranges = <0x0 0x00000000 0x0 0xffffffff>;
+			alignment = <0x0 0x400000>;
+			size = <0x0 0xc00000>;
+			reusable;
+		};
 	};
 
 	smp2p-adsp {