tu: Improve flushing on a7xx
a7xx renamed events around flushing:
a6xx a7xx
FLUSH CLEAN
INVALIDATE INVALIDATE
FLUSH+INVALIDATE FLUSH
The FLUSH events stayed the same but now they also invalidate. By not adopting the new CLEAN events, we're inadvertantly invalidating too much.
Change turnip to use the new names everywhere and use the CLEAN
events on a7xx.