Eat cycles during GE block transfers

Some adhoc tests showing the timing:
https://docs.google.com/spreadsheets/d/1nEo_mw7mcdqbdpsaZPdEHN_8ropzXayohoyRcQfishw/edit#gid=2054001637

This is enough to allow the gpu/commands/blocktransfer test to pass as current (before it didn't, even when run with non-null gpu, because it didn't reschedule on `sceGeDrawSync()`.)

-[Unknown]