drm/amd/display: clean up assignment of amdgpu_crtc

The declaration of pointer amdgpu_crtc has a redundant assignment to
amdgpu_crtc. Clean this up by removing it.

Detected by CoverityScan, CID#1460299 ("Evaluation order violation")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -3748,7 +3748,7 @@ static void remove_stream(struct amdgpu_device *adev,
 static int get_cursor_position(struct drm_plane *plane, struct drm_crtc *crtc,
 			       struct dc_cursor_position *position)
 {
-	struct amdgpu_crtc *amdgpu_crtc = amdgpu_crtc = to_amdgpu_crtc(crtc);
+	struct amdgpu_crtc *amdgpu_crtc = to_amdgpu_crtc(crtc);
 	int x, y;
 	int xorigin = 0, yorigin = 0;