iommu: Make some functions static

The sparse tool complains as follows:

drivers/iommu/iommu.c:386:5: warning:
 symbol 'iommu_insert_resv_region' was not declared. Should it be static?
drivers/iommu/iommu.c:2182:5: warning:
 symbol '__iommu_map' was not declared. Should it be static?

Those functions are not used outside of iommu.c, so mark them static.
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200713142542.50294-1-weiyongjun1@huawei.comSigned-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -383,8 +383,8 @@ static ssize_t iommu_group_show_name(struct iommu_group *group, char *buf)
  * Elements are sorted by start address and overlapping segments
  * of the same type are merged.
  */
-int iommu_insert_resv_region(struct iommu_resv_region *new,
-			     struct list_head *regions)
+static int iommu_insert_resv_region(struct iommu_resv_region *new,
+				    struct list_head *regions)
 {
 	struct iommu_resv_region *iter, *tmp, *nr, *top;
 	LIST_HEAD(stack);
@@ -2179,8 +2179,8 @@ static size_t iommu_pgsize(struct iommu_domain *domain,
 	return pgsize;
 }
 
-int __iommu_map(struct iommu_domain *domain, unsigned long iova,
-	      phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
+static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
+		       phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
 {
 	const struct iommu_ops *ops = domain->ops;
 	unsigned long orig_iova = iova;