driver core: Add a comment to set_primary_fwnode() on nullifying

Explain what parent && fn == parent->fwnode conditional does.
With this refactor the code a bit.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230323182640.61085-1-andriy.shevchenko@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -4982,8 +4982,12 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 	} else {
 		if (fwnode_is_primary(fn)) {
 			dev->fwnode = fn->secondary;
+
+			/* Skip nullifying fn->secondary if the primary is shared */
+			if (parent && fn == parent->fwnode)
+				return;
+
 			/* Set fn->secondary = NULL, so fn remains the primary fwnode */
-			if (!(parent && fn == parent->fwnode))
 			fn->secondary = NULL;
 		} else {
 			dev->fwnode = NULL;