iommu/arm-smmu: Mark qcom_smmu_client_of_match as possibly unused

When CONFIG_OF=n of_match_device() gets pre-processed out of existence
leaving qcom-smmu_client_of_match unused. Mark it as possibly unused to
keep the compiler from warning in that case.

Fixes: 0e764a01 ("iommu/arm-smmu: Allow client devices to select direct mapping")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200604203905.31964-1-jcrouse@codeaurora.orgSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/arm-smmu-qcom.c

@@ -12,7 +12,7 @@ struct qcom_smmu {
 	struct arm_smmu_device smmu;
 };
 
-static const struct of_device_id qcom_smmu_client_of_match[] = {
+static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
 	{ .compatible = "qcom,adreno" },
 	{ .compatible = "qcom,mdp4" },
 	{ .compatible = "qcom,mdss" },