Fails with raw data type none and NumericAddressedBackend

[mhier]

When having a NumericAddressedBackend it seems to always use getAsCoocked(), even if the accessor is not a raw accessor (because the raw data type is none). This may be an exotic corner case for now, which I can across when trying to get 64 bit floating point to work (for which raw access does not work currently as that is limited to 32 bit for now). Also I can imagine in future certain special registers might have no raw access even for the NumericAddressedBackend (e.g. void-like registers without data).