iommu/tegra: gart: Fix gart_iommu_unmap()

It must return the number of unmapped bytes on success, returning 0 means
that unmapping failed and in result only one page is unmapped.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/tegra-gart.c

@@ -313,7 +313,7 @@ static size_t gart_iommu_unmap(struct iommu_domain *domain, unsigned long iova,
 	gart_set_pte(gart, iova, 0);
 	FLUSH_GART_REGS(gart);
 	spin_unlock_irqrestore(&gart->pte_lock, flags);
-	return 0;
+	return bytes;
 }
 
 static phys_addr_t gart_iommu_iova_to_phys(struct iommu_domain *domain,