iommu/amd: Set variable amd_dirty_ops to static

Fix the followng warning:
drivers/iommu/amd/iommu.c:67:30: warning: symbol
 'amd_dirty_ops' was not declared. Should it be static?

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

Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231120095342.1102999-1-chentao@kylinos.cn
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: KunWuChan

drivers/iommu/amd/iommu.c

@@ -64,7 +64,7 @@ LIST_HEAD(hpet_map);
 LIST_HEAD(acpihid_map);
 
 const struct iommu_ops amd_iommu_ops;
-const struct iommu_dirty_ops amd_dirty_ops;
+static const struct iommu_dirty_ops amd_dirty_ops;
 
 int amd_iommu_max_glx_val = -1;
 
@@ -2635,7 +2635,7 @@ static bool amd_iommu_enforce_cache_coherency(struct iommu_domain *domain)
 	return true;
 }
 
-const struct iommu_dirty_ops amd_dirty_ops = {
+static const struct iommu_dirty_ops amd_dirty_ops = {
 	.set_dirty_tracking = amd_iommu_set_dirty_tracking,
 	.read_and_clear_dirty = amd_iommu_read_and_clear_dirty,
 };