lightrec: Run dynarec until next interrupt

lightrec: Run dynarec until next interrupt

Instead of running the dynarec once per block, which creates a huge
overhead as entering/exiting the dynarec isn't very fast, run only the
number of cycles until the next interrupt.

This boosts performance by a huge margin. On my PC, running the intro
video in MediEvil goes from using 34-36% CPU usage down to 16-17%.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Co-developed-by: notaz <notasas@gmail.com>
Signed-off-by: notaz <notasas@gmail.com>