Add missing DPU_CLK_CTRL_WB2 to sc7180_mdp clocks array.

Fixes: 51e4d60e ("drm/msm/dpu: add writeback support for sc7180")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Tested-by: Jessica Zhang <quic_jesszhan@quicinc.com> # Trogdor (sc7180)
Patchwork: https://patchwork.freedesktop.org/patch/518504/
Link: https://lore.kernel.org/r/20230116103055.780767-1-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>