drm/amdgpu: use adev_to_drm to get drm device

adev_to_drm is used everywhere in amdgpu code, so modify
it to keep consistency.
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c

@@ -402,7 +402,7 @@ static void amdgpu_ctx_fini(struct kref *ref)
 		}
 	}
 
-	if (drm_dev_enter(&adev->ddev, &idx)) {
+	if (drm_dev_enter(adev_to_drm(adev), &idx)) {
 		amdgpu_ctx_set_stable_pstate(ctx, ctx->stable_pstate);
 		drm_dev_exit(idx);
 	}