device property: Add fwnode_graph_get_endpoint_by_id()

fwnode_graph_get_endpoint_by_id() is intended for obtaining local
endpoints by a given local port.

fwnode_graph_get_endpoint_by_id() is slightly different from its OF
counterpart, of_graph_get_endpoint_by_regs(): instead of using -1 as
a value to indicate that a port or an endpoint number does not matter,
it uses flags to look for equal or greater endpoint. The port number
is always fixed. It also returns only remote endpoints that belong
to an available device, a behaviour that can be turned off with a flag.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>