iommu: Mark __iommu_map_sg() as static

Now __iommu_map_sg() is used only in iommu.c file, so mark it static.
Signed-off-by: NBaolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: NWill Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/ab722e9970739929738066777b8ee7930e32abd5.1591930156.git.baolin.wang@linux.alibaba.comSigned-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -2330,9 +2330,9 @@ size_t iommu_unmap_fast(struct iommu_domain *domain,
 }
 EXPORT_SYMBOL_GPL(iommu_unmap_fast);
 
-size_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
-		    struct scatterlist *sg, unsigned int nents, int prot,
-		    gfp_t gfp)
+static size_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
+			     struct scatterlist *sg, unsigned int nents, int prot,
+			     gfp_t gfp)
 {
 	size_t len = 0, mapped = 0;
 	phys_addr_t start;