drm/amdgpu: change pointer of mqd_ptr & mqd_backup to void

vi_mqd is only used by VI family but mqd_ptr and mqd_backup is
common for all ASIC, so change the pointer to void.

Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Monk Liu <Monk.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
index 5d0f7c5..da702dc 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
@@ -162,7 +162,7 @@ struct amdgpu_ring {
 	u32			queue;
 	struct amdgpu_bo	*mqd_obj;
 	uint64_t                mqd_gpu_addr;
-	struct vi_mqd           *mqd_ptr;
+	void                    *mqd_ptr;
 	u32			doorbell_index;
 	bool			use_doorbell;
 	unsigned		wptr_offs;