sw64: iommu: allow unlimited minimum value of iova in unmanaged domain

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56OLG

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IO virtual address assignment in unmanaged domain is completely handed
over to the device owner, so there is no need to set the IOVA baseline.
Signed-off-by: NZhou Xuemei <zhouxuemei@wxiat.com>
Signed-off-by: NGu Zitao <guzitao@wxiat.com>

drivers/iommu/sw64/sunway_iommu.c

@@ -1382,7 +1382,7 @@ static struct iommu_domain *sunway_iommu_domain_alloc(unsigned type)
 
 		sdomain->pt_root = (void *)get_zeroed_page(GFP_KERNEL);
 
-		sdomain->domain.geometry.aperture_start = SW64_DMA_START;
+		sdomain->domain.geometry.aperture_start = 0ULL;
 		sdomain->domain.geometry.aperture_end	= (~0ULL);
 		sdomain->domain.geometry.force_aperture	= true;
 		sdomain->type = IOMMU_DOMAIN_UNMANAGED;