device property: Constify a few fwnode APIs

The fwnode parameter is not altered in the following APIs:

- fwnode_get_next_parent_dev()
- fwnode_is_ancestor_of()
- fwnode_graph_get_endpoint_count()

so constify them.

Reported-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230324112720.71315-1-andriy.shevchenko@linux.intel.com


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