drm/msm/dpu: use devres-managed allocation for MDP TOP

Use devm_kzalloc to create MDP TOP structure. This allows us to remove
corresponding kfree and drop dpu_hw_mdp_destroy() function.

Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/570047/
Link: https://lore.kernel.org/r/20231201211845.1026967-6-dmitry.baryshkov@linaro.org