of: kobj: export of_node_ktype for use by modules

of_node_init() is a static inline that references of_node_ktype when
CONFIG_OF_KOBJ=y. Any module that calls of_node_init() will therefore
have an unresolved reference to of_node_ktype at load time, because
the symbol is defined in drivers/of/kobj.c but was never exported.

This causes a modpost build error when CONFIG_OF_KOBJ=y and
CONFIG_DRIVER_PE_KUNIT_TEST=m:

  ERROR: modpost: "of_node_ktype"
  [drivers/base/test/property-entry-test.ko] undefined!

Add EXPORT_SYMBOL_IF_KUNIT(of_node_ktype) so that modules such as the
KUnit property-entry test can call of_node_init() without hitting this
linker error.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202607181651.RnUuV8n6-lkp@intel.com/
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202607181651.RnUuV8n6-lkp@intel.com/
Link: https://patch.msgid.link/20260721105448.2109894-2-xu.yang_2@oss.nxp.com
[ Add empty line before the kunit include. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

drivers/of/kobj.c

@@ -2,6 +2,8 @@
 #include <linux/of.h>
 #include <linux/slab.h>
 
+#include <kunit/visibility.h>
+
 #include "of_private.h"
 
 /* true when node is initialized */
@@ -27,6 +29,7 @@ static void of_node_release(struct kobject *kobj)
 const struct kobj_type of_node_ktype = {
 	.release = of_node_release,
 };
+EXPORT_SYMBOL_IF_KUNIT(of_node_ktype);
 
 static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj,
 				const struct bin_attribute *bin_attr, char *buf,