Refactor CPU mutex code

src/cpu/interrupt.c

@@ -33,7 +33,7 @@ void interrupt_trigger(rv32_cpu_t* cpu, uint32_t scause)
 	// but we know it is not in the middle of an instruction
 	// (we got the mutex) ; this way we can just change
 	// registers to set interrupt handler execution
-	pthread_mutex_lock(&cpu0_mutex);
+	pthread_mutex_lock(&cpu->mutex);
 
 	// Set xCAUSE with interrupt bit set
 	cpu->csr[CSR_SCAUSE] = 0x80000000 | scause;
@@ -67,7 +67,7 @@ void interrupt_trigger(rv32_cpu_t* cpu, uint32_t scause)
 			break;
 	}
 
-	pthread_mutex_unlock(&cpu0_mutex);
+	pthread_mutex_unlock(&cpu->mutex);
 }
 
 void interrupt_timer_thread()