drm/msm/adreno: Use quirk to identify cached-coherent support

It is better to explicitly list it.  With the move to opaque chip-id's
for future devices, we should avoid trying to infer things like
generation from the numerical value.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/549765/