rv32cpu: allocated with calloc (for debug)

src/cpu/rv32cpu.c

@@ -39,7 +39,7 @@ static void cpu_print_instruction(instruction_t* instruction);
 
 void cpu_init()
 {
-	cpu0 = malloc(sizeof(rv32_cpu_t));
+	cpu0 = calloc(1, sizeof(rv32_cpu_t));
 	cpu0->regs.zero = 0;
 }