Reindents membus.cpp
LY register is 'correctly' updated, but only works when cpu isn't limited

I think this is because the LY is updated quite steadily, but our cpu,
when limited, only reads from LY every now and then: chances are pretty
slim that it reads the value it wants from LY... without the limiter,
the cpu constantly reads from LY, so that's great -- but way too fast.