media: saa7134: use sg_dma_len when building pgtable

The new AMD IOMMU DMA implementation concatenates sglist entries under
certain conditions, and because saa7134 accessed the length member
directly, it did not support this scenario.

This fixes IO_PAGE_FAULTs and choppy DMA audio by using the
sg_dma_len macro.

Fixes: be62dbf5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api")
Signed-off-by: NTasos Sahanidis <tasos@tasossah.com>
Signed-off-by: NHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/pci/saa7134/saa7134-core.c

@@ -243,7 +243,7 @@ int saa7134_pgtable_build(struct pci_dev *pci, struct saa7134_pgtable *pt,
 
 	ptr = pt->cpu + startpage;
 	for (i = 0; i < length; i++, list = sg_next(list)) {
-		for (p = 0; p * 4096 < list->length; p++, ptr++)
+		for (p = 0; p * 4096 < sg_dma_len(list); p++, ptr++)
 			*ptr = cpu_to_le32(sg_dma_address(list) +
 						list->offset + p * 4096);
 	}