media: device property: Define format macros for ports and endpoints

OF, ACPI and software_nodes all implement graphs including nodes for ports
and endpoints. These are all intended to be named with a common schema,
as "port@n" and "endpoint@n" where n is an unsigned int representing the
index of the node. To ensure commonality across the subsystems, provide a
set of macros to define the format.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <djrscally@gmail.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>