of: iommu: make of_iommu_init() postcore_initcall_sync

The of_iommu_init() is called multiple times by arch code,
make it postcore_initcall_sync, then we can drop relevant
calls fully.

Note, the IOMMUs should have a chance to perform some basic
initialisation before we start adding masters to them. So
postcore_initcall_sync is good choice, it ensures of_iommu_init()
called before of_platform_populate.

Acked-by: Rich Felker <dalias@libc.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/iommu/of_iommu.c

@@ -174,7 +174,7 @@ err_put_node:
 	return NULL;
 }
 
-void __init of_iommu_init(void)
+static int __init of_iommu_init(void)
 {
 	struct device_node *np;
 	const struct of_device_id *match, *matches = &__iommu_of_table;
@@ -186,4 +186,7 @@ void __init of_iommu_init(void)
 			pr_err("Failed to initialise IOMMU %s\n",
 				of_node_full_name(np));
 	}
+
+	return 0;
 }
+postcore_initcall_sync(of_iommu_init);