drm/amdgpu: fix amdgpu_move_blit on 32bit systems

BugLink: http://bugs.launchpad.net/bugs/1621113

commit 815d27a4 upstream.

This bug seems to be present for a very long time.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

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

@@ -233,8 +233,8 @@ static int amdgpu_move_blit(struct ttm_buffer_object *bo,
 
 	adev = amdgpu_get_adev(bo->bdev);
 	ring = adev->mman.buffer_funcs_ring;
-	old_start = old_mem->start << PAGE_SHIFT;
-	new_start = new_mem->start << PAGE_SHIFT;
+	old_start = (u64)old_mem->start << PAGE_SHIFT;
+	new_start = (u64)new_mem->start << PAGE_SHIFT;
 
 	switch (old_mem->mem_type) {
 	case TTM_PL_VRAM: