iommu/exynos: Use the devm_clk_get_optional() helper

Use devm_clk_get_optional() instead of hand writing it.
This saves some loC and improves the semantic.

Signed-off-by: Christophe JAILLET <[e-mail]>
Acked-by: Marek Szyprowski <[e-mail]>
Link: https://lore.kernel.org/r/99c0d5ce64[e-mail]
Signed-off-by: Joerg Roedel <[e-mail]>

drivers/iommu/exynos-iommu.c

···
 		return ret;
 	}
 
-	data->clk = devm_clk_get(dev, "sysmmu");
-	if (PTR_ERR(data->clk) == -ENOENT)
-		data->clk = NULL;
-	else if (IS_ERR(data->clk))
+	data->clk = devm_clk_get_optional(dev, "sysmmu");
+	if (IS_ERR(data->clk))
 		return PTR_ERR(data->clk);
 
-	data->aclk = devm_clk_get(dev, "aclk");
-	if (PTR_ERR(data->aclk) == -ENOENT)
-		data->aclk = NULL;
-	else if (IS_ERR(data->aclk))
+	data->aclk = devm_clk_get_optional(dev, "aclk");
+	if (IS_ERR(data->aclk))
 		return PTR_ERR(data->aclk);
 
-	data->pclk = devm_clk_get(dev, "pclk");
-	if (PTR_ERR(data->pclk) == -ENOENT)
-		data->pclk = NULL;
-	else if (IS_ERR(data->pclk))
+	data->pclk = devm_clk_get_optional(dev, "pclk");
+	if (IS_ERR(data->pclk))
 		return PTR_ERR(data->pclk);
 
 	if (!data->clk && (!data->aclk || !data->pclk)) {
···
 		return -ENOSYS;
 	}
 
-	data->clk_master = devm_clk_get(dev, "master");
-	if (PTR_ERR(data->clk_master) == -ENOENT)
-		data->clk_master = NULL;
-	else if (IS_ERR(data->clk_master))
+	data->clk_master = devm_clk_get_optional(dev, "master");
+	if (IS_ERR(data->clk_master))
 		return PTR_ERR(data->clk_master);
 
 	data->sysmmu = dev;