When copying/blitting with format reinterpretation, we invalidate the
texture cache before/after.  Before is so the source of the copy works,
and after is to get rid of our new data in the "wrong" format to protect
future attempts to sample.

When I ported these hacks to iris, I tried to be cautious by only
bothering with the hacks if the batch referenced the BO.  This makes
some sense for the before case.  If it isn't referenced, the texture
cache can't really have any data for the BO (since it's also invalidated
between batches).  But we still need to do the after case regardless,
as we've just polluted the cache with hazardous entries.