drm/msm/dpu: drop separate dpu_core_perf_tune overrides

The values in struct dpu_core_perf_tune are fixed per the core perf
mode. Drop the 'tune' values and substitute them with known values when
performing perf management.

Note: min_bus_vote was not used at all, so it is just silently dropped.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/550208/
Link: https://lore.kernel.org/r/20230730010102.350713-4-dmitry.baryshkov@linaro.org