swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single

swiotlb_tbl_map_single currently nevers sets a tlb_addr that is not
aligned to the tlb bucket size.  But we're going to add such a case
soon, for which this adjustment would be bogus.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jianxiong Gao <jxgao@google.com>
Tested-by: Jianxiong Gao <jxgao@google.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>