Keep all interrupt priorities to Set to keep it simple.
The original intent was assumption that when we get next DOI
interrupt while we are already processing one, we dont need
the next DOI to be set again... This is highly theoretical,
not proven, and total cornercase where we would need to hit
very tiny timing interval by clearing DOI interrupt...
Altough it might be true that in such a case clear is more
beneficial, it is not worthy the additional cost...