In a few cases the functionality of fwnode_for_each_parent_node()
is already in use. Introduce a common helper macro for it.

It may be used by others as well in the future.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>