iommu/exynos: Fix error handling for of_platform_device_create

of_platform_device_create returns NULL on error so an IS_ERR test is
incorrect here and a NULL check is required.

The Coccinelle semantic patch used to make this change is as follows:
@@
expression e;
@@

  e = of_platform_device_create(...);
if(
-    IS_ERR(e)
+    !e
    )
    {
  <+...
  return
- PTR_ERR(e)
+ -ENODEV
  ;
  ...+>
  }

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>