adding printf regression test

tests/regression/printf/kernel.c

@@ -0,0 +1,15 @@
+#include <stdint.h>
+#include <vx_intrinsics.h>
+#include <vx_spawn.h>
+#include "common.h"
+
+void kernel_body(int task_id, void* arg) {
+	struct kernel_arg_t* _arg = (struct kernel_arg_t*)(arg);
+	int* src_ptr = (int*)_arg->src_ptr;
+	vx_printf("task=%d, value=%d\n", task_id, src_ptr[task_id]);
+}
+
+void main() {
+	struct kernel_arg_t* arg = (struct kernel_arg_t*)KERNEL_ARG_DEV_MEM_ADDR;
+	vx_spawn_tasks(arg->num_points, kernel_body, arg);
+}