Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c: In function _dpu_danger_signal_status:
drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c:80:26: warning: variable priv set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c: In function dpu_kms_prepare_commit:
drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c:271:26: warning: variable priv set but not used [-Wunused-but-set-variable]

It is not used since commit 25fdd593 ("drm/msm:
Add SDM845 DPU support")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NRob Clark <robdclark@chromium.org>