[PATCH -next] drm/amd/display: Fix unused variable warning

[Wei Yongjun]

GCC reports the following warning with W=1:

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:5439:33:
 warning: unused variable 'dm' [-Wunused-variable]
 5439 |  struct amdgpu_display_manager *dm = &adev->dm;
      |                                 ^~

This variable only used when CONFIG_DRM_AMD_DC_DCN is set, this
commit fix the warning.

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index e24a13fd2730..bda8d5f4e56a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5436,8 +5436,8 @@ static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
 	struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
 	struct amdgpu_device *adev = drm_to_adev(crtc->dev);
 	struct dm_crtc_state *acrtc_state = to_dm_crtc_state(crtc->state);
-	struct amdgpu_display_manager *dm = &adev->dm;
 #if defined(CONFIG_DRM_AMD_DC_DCN)
+	struct amdgpu_display_manager *dm = &adev->dm;
 	unsigned long flags;
 #endif
 	int rc = 0;