Disabling interrupts before entering sleepstates.

This didn't work properly before but seems to work fine now.
Also added a panic for now, to find out if it is an issue atm.

src/add-ons/kernel/bus_managers/acpi/BusManager.cpp

@@ -678,7 +678,10 @@ enter_sleep_state(uint8 state, uint8 flags)
 
 	TRACE("enter_sleep_state %d with flags %d\n", state, flags);
 
+	cpu_status cpu = disable_interrupts();
 	status = AcpiEnterSleepState(state, flags);
+	restore_interrupts(cpu);
+	panic("AcpiEnterSleepState should not return.");
 	if (status != AE_OK)
 		return B_ERROR;