Splits DVD reads up into smaller chunks so that data is available
before the final interrupt is triggered. This better simulates the DMA
that happens on a real device, which some games will take advantage of -
by either playing back data as it is loading or by using data that is
going to be overwritten shortly by an outstanding read.
Simplification/reduction of duplicated code. Detect other constant GQR values and inline loads (5-10% speedup) and do direct dispatch to AOT methods for stores.