drm/msm/a6xx: Add missing regs for A7XX

Add some missing definitions required for A7 support.

This may be substituted with a mesa header sync.

Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # sm8450
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/559282/
Signed-off-by: Rob Clark <robdclark@chromium.org>