SMC100: Motion setpoints PVs in alarm

During a support call on LOQ (fixing the DLS sample changer) we noticed that the motion setpoints PVs for `POSN` and `POSITIONED` were in link alarm which was causing the blocks set on these PVs to also be in alarm and therefore show "invalid" instead of their values. A workaround for this exists in the GUI preferences to show the value regardless, but we should fix the underlying issue causing those PVs to go into alarm.

### Acceptance criteria
- [ ] Above issue is fixed. It may be that we need a real SMC100 to test this.

Additional info
To replicate you could use the DLS sample component from LOQ with the motionsetpoints.cmd file and dls_sample_changer.txt from their settings area (SMC100\ and motionsetpoints\ respectively)
We think this may be because the device does not poll when not moving, but are unsure. As it is in link alarm it could be a FLNK not correctly forwarding something.

Riproduci il problema utilizzando il componente di esempio DLS di LOQ, insieme a motionsetpoints.cmd e dls_sample_changer.txt dall’area delle impostazioni. Verifica perché le PVs dei setpoint di movimento POSN e POSITIONED entrano in allarme di collegamento, incluso se sono coinvolti polling o FLNK forwarding. Il lavoro è completato quando queste PVs e i relativi blocchi non mostrano più allarmi o valori non validi.

Scritto dal modello di indicizzazione a partire dal testo della issue.