device property: Clarify description of returned value in some functions

Some of the functions do not provide Return: section on absence of which
kernel-doc complains. Besides that several functions return the fwnode
handle with incremented reference count. Add a respective note to make sure
that the caller decrements it when it's not needed anymore.

While at it, unify the style of the Return: sections.
Reported-by: Daniel Kaehn <kaehndan@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230217133344.79278-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>