drm/msm/dpu: Clear CTL_FETCH_PIPE_ACTIVE before blend setup

drm/msm/dpu: Clear CTL_FETCH_PIPE_ACTIVE before blend setup

Before blend setup, all existing blend stages are cleared, so shall be
active fetch pipes.

Fixes: b3652e87c03c ("drm/msm/disp/dpu1: add support to program fetch active in ctl path")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/651263/
Link: https://lore.kernel.org/r/20250430-b4-sm8750-display-v5-10-8cab30c3e4df@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>