sepolicy: Add rules for property access for WFD

-- WFD debug properties are now prefixed with vendor keyword.
-- With no property contexts defined, accessing such vendor*
   properties are prohibited in system
-- Hence, creating a property context for all WFD debug properties
   and granting wfdservice permission to access the same

Change-Id: I04f7cf350dfff5f316edfbf1434062ae2ef8e5f9