iommu/tegra241-cmdqv: Staticize cmdqv_debugfs_dir

Fix a sparse warning.

Fixes: 918eb5c ("iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410172003.bRQEReTc-lkp@intel.com/
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20241021230847.811218-1-nicolinc@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: nicolinc

drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c

@@ -800,7 +800,7 @@ static int tegra241_cmdqv_init_structures(struct arm_smmu_device *smmu)
 	return 0;
 }
 
-struct dentry *cmdqv_debugfs_dir;
+static struct dentry *cmdqv_debugfs_dir;
 
 static struct arm_smmu_device *
 __tegra241_cmdqv_probe(struct arm_smmu_device *smmu, struct resource *res,