drm/msm/dpu: move struct dpu_hw_blk definition to dpu_hw_utils.h

There is little point in having a separate header just for a single
opaque struct definition. Drop it now and move the struct to the
dpu_hw_util.h header.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/488016/
Link: https://lore.kernel.org/r/20220601161349.1517667-5-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>