iommu/vt-d: Set variable intel_dirty_ops to static

Fix the following warning:
drivers/iommu/intel/iommu.c:302:30: warning: symbol
 'intel_dirty_ops' was not declared. Should it be static?

This variable is only used in its defining file, so it should be static.

Fixes: f35f22c ("iommu/vt-d: Access/Dirty bit support for SS domains")
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20231120101025.1103404-1-chentao@kylinos.cn
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel/iommu.c

@@ -299,7 +299,7 @@ static int iommu_skip_te_disable;
 #define IDENTMAP_AZALIA		4
 
 const struct iommu_ops intel_iommu_ops;
-const struct iommu_dirty_ops intel_dirty_ops;
+static const struct iommu_dirty_ops intel_dirty_ops;
 
 static bool translation_pre_enabled(struct intel_iommu *iommu)
 {
@@ -4929,7 +4929,7 @@ static int intel_iommu_read_and_clear_dirty(struct iommu_domain *domain,
 	return 0;
 }
 
-const struct iommu_dirty_ops intel_dirty_ops = {
+static const struct iommu_dirty_ops intel_dirty_ops = {
 	.set_dirty_tracking = intel_iommu_set_dirty_tracking,
 	.read_and_clear_dirty = intel_iommu_read_and_clear_dirty,
 };