ACPI: property: graph: Fix graph documentation

Address a few issues in the ACPI _DSD properties graph documentation:

 - the extension for port nodes is a data extension (and not property
   extension),

 - clean up language in port hierarchical data extension definition,

 - add examples of port and endpoint packages,

 - port property value is the number of the "port" and not the number
   of the "port node",

 - remove word "individual" from endpoint data node description, it
   was redundant,

 - remove the extra "The" in the endpoint property description,

 - refer to hierarchical data extension keys and targets instead of
   first and second package list entries.

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