radv: Try to do a better job of dealing with L2 coherent images.

Only try to invalidate L2 if we actually hit one of the incoherent images.

Note we may actually insert some extra flushes at the end of a command buffer so that we may asume the caches are clean the start of the next command buffer. However, on average I think that case is uncommon enough that being able to make assumptions at the start of a cmdbuffer is beneficial. Especially since MSAA is somewhat rare in more recent games.

In practice I've gotten the number of L2 flushes significantly down in some tests.