tests: add missing gpu kernels

tests/gpu_kernels.cu

+#include <cstdint>
+#include <cstdio>
+
+#include <cuda.h>
+#include <cuda_runtime.h>
+
+#include <villas/gpu.hpp>
+#include <villas/fpga/ips/rtds2gpu.hpp>
+
+
+
+__global__ void
+gpu_rtds_rtt_kernel(volatile uint32_t* dataIn, volatile reg_doorbell_t* doorbellIn,
+                    volatile uint32_t* dataOut, volatile villas::fpga::ip::ControlRegister* controlRegister,
+                    int* run)
+{
+	printf("[gpu] gpu kernel go\n");
+
+	printf("dataIn:      %p\n", dataIn);
+	printf("doorbellIn:  %p\n", doorbellIn);
+	printf("dataOut:     %p\n", dataOut);
+	printf("control:     %p\n", controlRegister);
+	printf("run:         %p\n", run);
+
+//	*run = reinterpret_cast<bool*>(malloc(sizeof(bool)));
+//	**run = true;
+
+	uint32_t last_seq;
+	while(*run) {
+		// wait for data
+//		printf("[gpu] wait for data, last_seq=%u\n", last_seq);
+		while(not (doorbellIn->is_valid and (last_seq != doorbellIn->seq_nr)) and *run);
+//			printf("doorbell: 0x%08x\n", doorbellIn->value);
+
+		last_seq = doorbellIn->seq_nr;
+
+//		printf("[gpu] copy data\n");
+		for(size_t i = 0; i < doorbellIn->count; i++) {
+			dataOut[i] = dataIn[i];
+		}
+
+		// reset doorbell
+//		printf("[gpu] reset doorbell\n");
+//		doorbellIn->value = 0;
+
+//		printf("[gpu] signal go for gpu2rtds\n");
+		controlRegister->ap_start = 1;
+	}
+
+	printf("kernel done\n");
+}
+
+static int* run = nullptr;
+
+void gpu_rtds_rtt_start(volatile uint32_t* dataIn, volatile reg_doorbell_t* doorbellIn,
+                        volatile uint32_t* dataOut, volatile villas::fpga::ip::ControlRegister* controlRegister)
+{
+	printf("run:         %p\n", run);
+	if(run == nullptr) {
+		run = (int*)malloc(sizeof(uint32_t));
+		cudaHostRegister(run, sizeof(uint32_t), 0);
+	}
+	printf("run:         %p\n", run);
+
+
+	*run = 1;
+	gpu_rtds_rtt_kernel<<<1, 1>>>(dataIn, doorbellIn, dataOut, controlRegister, run);
+	printf("[cpu] kernel launched\n");
+}
+
+void gpu_rtds_rtt_stop()
+{
+	*run = 0;
+	cudaDeviceSynchronize();
+}