freedreno: track batch/blit types

freedreno: track batch/blit types

Add a bit of extra book-keeping about blits and back-blits (from
resource shadowing).  If the app uploads all mipmap levels, as opposed
to uploading the first level and then glGenerateMipmap(), we can discard
the back-blit (as opposed to being naive and shadowing the resource for
each mipmap level).  Also, after a normal blit, we might as well flush
the batch immediately, since there is not likely to be further rendering
to the surface.

Signed-off-by: Rob Clark <robdclark@gmail.com>