drivers: of/base: move of_init to driver_init

Commit 5590f3196b29 ("drivers/core/of: Add symlink to device-tree from
devices with an OF node") adds the symlink `of_node` for each device
pointing to it's device tree node while creating/initialising it.

However the devicetree sysfs is created and setup in of_init which is
executed at core_initcall level. For all the devices created before
of_init, the following error is thrown:
	"Error -2(-ENOENT) creating of_node link"

Like many other components in driver model, initialize the sysfs support
for OF/devicetree from driver_init so that it's ready before any devices
are created.

Fixes: 5590f3196b29 ("drivers/core/of: Add symlink to device-tree from
	devices with an OF node")
Suggested-by: Rob Herring <robh+dt@kernel.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Robert Schwebel <r.schwebel@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 99764db..f065026 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -189,7 +189,7 @@
 	return 0;
 }
 
-static int __init of_init(void)
+void __init of_core_init(void)
 {
 	struct device_node *np;
 
@@ -198,7 +198,8 @@
 	of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
 	if (!of_kset) {
 		mutex_unlock(&of_mutex);
-		return -ENOMEM;
+		pr_err("devicetree: failed to register existing nodes\n");
+		return;
 	}
 	for_each_of_allnodes(np)
 		__of_attach_node_sysfs(np);
@@ -207,10 +208,7 @@
 	/* Symlink in /proc as required by userspace ABI */
 	if (of_root)
 		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
-
-	return 0;
 }
-core_initcall(of_init);
 
 static struct property *__of_find_property(const struct device_node *np,
 					   const char *name, int *lenp)