drm/msm/mdp5: Eliminate useless code

Since mdp5_state is initialized twice at the same time, so
we make code simple and easy to understand by delete one.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/482500/
Link: https://lore.kernel.org/r/1650348980-19050-1-git-send-email-baihaowen@meizu.com


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