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/include/linux/of.h b/include/linux/of.h
index ddeaae6..b871ff9 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -121,6 +121,8 @@
 extern raw_spinlock_t devtree_lock;
 
 #ifdef CONFIG_OF
+void of_core_init(void);
+
 static inline bool is_of_node(struct fwnode_handle *fwnode)
 {
 	return fwnode && fwnode->type == FWNODE_OF;
@@ -376,6 +378,10 @@
 
 #else /* CONFIG_OF */
 
+static inline void of_core_init(void)
+{
+}
+
 static inline bool is_of_node(struct fwnode_handle *fwnode)
 {
 	return false;