x86/amd_gart: don't set failed sg dma_address to DMA_MAPPING_ERROR

Setting the ->dma_address to DMA_MAPPING_ERROR is not part of
the ->map_sg calling convention, so remove it.

Link: https://lore.kernel.org/linux-mips/20210716063241.GC13345@lst.de/Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/x86/kernel/amd_gart_64.c

@@ -458,8 +458,6 @@ static int gart_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		panic("dma_map_sg: overflow on %lu pages\n", pages);
 
 	iommu_full(dev, pages << PAGE_SHIFT, dir);
-	for_each_sg(sg, s, nents, i)
-		s->dma_address = DMA_MAPPING_ERROR;
 	return ret;
 }