drm/msm/mdp5: drop global_state_lock

drm/msm/mdp5: drop global_state_lock

Since the commit b962a12050a3 ("drm/atomic: integrate modeset lock with
private objects") the DRM framework no longer requires the external
lock for private objects. Drop the lock, letting the DRM to manage
private object locking.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/570183/
Link: https://lore.kernel.org/r/20231203000532.1290480-6-dmitry.baryshkov@linaro.org