drm/msm/dpu: Fix compile warnings

Using the following command will get compile warnings:
make W=1 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.o ARCH=arm64

drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘_dpu_crtc_program_lm_output_roi’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:91:19: warning: variable
‘dpu_crtc’ set but not used [-Wunused-but-set-variable]
  struct dpu_crtc *dpu_crtc;
                   ^~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘dpu_crtc_atomic_begin’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:428:35: warning: variable
‘smmu_state’ set but not used [-Wunused-but-set-variable]
  struct dpu_crtc_smmu_state_data *smmu_state;
                                   ^~~~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘dpu_crtc_atomic_flush’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:489:25: warning: variable
‘event_thread’ set but not used [-Wunused-but-set-variable]
  struct msm_drm_thread *event_thread;
                         ^~~~~~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘dpu_crtc_destroy_state’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:565:19: warning: variable
‘dpu_crtc’ set but not used [-Wunused-but-set-variable]
  struct dpu_crtc *dpu_crtc;
                   ^~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘dpu_crtc_duplicate_state’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:664:19: warning: variable
‘dpu_crtc’ set but not used [-Wunused-but-set-variable]
  struct dpu_crtc *dpu_crtc;
                   ^~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function
‘dpu_crtc_disable’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:693:26: warning: variable
‘priv’ set but not used [-Wunused-but-set-variable]
  struct msm_drm_private *priv;
                          ^~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:691:27: warning: variable
‘mode’ set but not used [-Wunused-but-set-variable]
  struct drm_display_mode *mode;
                           ^~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function ‘dpu_crtc_enable’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:766:26: warning: variable
‘priv’ set but not used [-Wunused-but-set-variable]
  struct msm_drm_private *priv;
                          ^~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c: In function ‘dpu_crtc_init’:
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:1292:18: warning: variable
‘kms’ set but not used [-Wunused-but-set-variable]
  struct dpu_kms *kms = NULL;
                  ^~~
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:663: warning: Excess function
parameter 'Returns' description in 'dpu_crtc_duplicate_state'

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Hongbo Yao <yaohongbo@huawei.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>