freedreno/a6xx: UBWC support for images

freedreno/a6xx: UBWC support for images

There are still some fallbacks we'll need to handle before we can enable
UBWC by default.  I think we may need to fallback to uncompressed if
image atomic operations are used.  And we still need to sort out how to
handle image and sampler views of compressed resources if the image/
sampler view is using a format that does not support compression.  (I
think the latter should hopefully be uncommon outside of deqp/piglit.)

But at least this gets us to the point where supertuxkart works properly
with UBWC enabled ;-)

Signed-off-by: Rob Clark <robdclark@chromium.org>