device property: Make fwnode_graph_for_each_endpoint() consistent

Make fwnode_graph_for_each_endpoint() consistent with the rest of
for_each_*() definitions in the file, i.e. use the form of

	for (iter = func(NULL); iter; \
	     iter = func(iter))

as it's done in all the rest of the similar macro definitions.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20230117152120.42531-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>