iommu/tegra-smmu: Use devm_bitmap_zalloc when applicable

'smmu->asids' is a bitmap. So use 'devm_kzalloc()' to simplify code,
improve the semantic of the code and avoid some open-coded arithmetic in
allocator arguments.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/2c0f4da80c3b5ef83299c651f69a563034c1c6cb.1632661557.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/tegra-smmu.c

@@ -1079,7 +1079,6 @@ struct tegra_smmu *tegra_smmu_probe(struct device *dev,
 				    struct tegra_mc *mc)
 {
 	struct tegra_smmu *smmu;
-	size_t size;
 	u32 value;
 	int err;
 
@@ -1097,9 +1096,7 @@ struct tegra_smmu *tegra_smmu_probe(struct device *dev,
 	 */
 	mc->smmu = smmu;
 
-	size = BITS_TO_LONGS(soc->num_asids) * sizeof(long);
-
-	smmu->asids = devm_kzalloc(dev, size, GFP_KERNEL);
+	smmu->asids = devm_bitmap_zalloc(dev, soc->num_asids, GFP_KERNEL);
 	if (!smmu->asids)
 		return ERR_PTR(-ENOMEM);