Eurotherm: handle write above hard limit

The Eurotherm device has "soft limits" for the SP, which you can set on the device itself ("SP L" and "SP H"), but it has also "hard limits" (e.g. I can't set the SP H higher than 99.9).

When the SP PV is set outside of the soft limit range, the device returns a Limit Error, which we read in the ERR PV. However, if we set it outside the hard limit, the device simply doesn't give any reply confirmation message at all and the PV times out.

This holds not only for the SP PV, but for the other write PVs too (e.g. P, I, D). Should we somehow capture that in another error PV? (Note that the PVs affected would go on a timeout alarm status)