drm/msm/a690: Remove revn and name

These fields are deprecated.  But any userspace new enough to support
a690 also knows how to identify the GPU based on chip-id.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/545552/