Hack fix for CDROM timings regression (Castlevania, Megaman X4)

See https://github.com/libretro/pcsx_rearmed/issues/557.

The CDROM timings changes from Redux fixed a bunch of games
(Crash Team Racing's intro no longer cuts off too early,
Worms Pinball gets further instead of just crashing,
FF8 Lunar Cry FMV no longer crashes etc...)
but it broke the other games that relied on ADPCM samples,
which is most noticeable in games like Castlevania or Megaman X4.

According to nicolasnoble, we should not cause a delay if seek destination is close to the current location.
However, this would require a lot more work so in the meantime,
let's do just that and add a comment.