Slow DDR2 reading

That is was I was starting to suspect, that this is the normal behaviour, and that the best idea is to use bursts. I was trying to avoid it for simplicity, and due to the odd number of words... but well, I will have to read 256 words and ignore the last one (also not taking it into account to update the counters), or do burst readings except for the last words. Perhaps it is even better to also write a dummy word so all addresses are ever aligned to power of two boundaries.