xen/swiotlb: fix stale reference to swiotlb_unmap_page()

Commit af85de5 ("xen: swiotlb: Switch to physical
address mapping callbacks") renamed xen_swiotlb_unmap_page()
to xen_swiotlb_unmap_phys().  The comment in
xen_swiotlb_unmap_sg() had already been missing the xen_
prefix (reading swiotlb_unmap_page()), and the rename only
changed _page to _phys without correcting this, leaving it
as swiotlb_unmap_phys().  Fix the reference to use the
correct function name xen_swiotlb_unmap_phys().

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260321110039.8905-1-kexinsun@smail.nju.edu.cn>

Author: Kexin Sun

drivers/xen/swiotlb-xen.c

@@ -340,7 +340,7 @@ xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
 
 /*
  * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
- * concerning calls here are the same as for swiotlb_unmap_phys() above.
+ * concerning calls here are the same as for xen_swiotlb_unmap_phys() above.
  */
 static void
 xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,