drm/msm/dpu: Remove set but not used variable 'priv' in dpu_kms.c

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: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>