Drop support for old association interface

A new association interface is defined in phosphor-dbus-interfaces
It would be nice to move the local version of the interface
to the new one.

The behavior of how association work is described here:
https://github.com/openbmc/docs/blob/master/object-mapper.md#associations

I did some searching and confirmed that all the old interfaces
(except the openbmc/pyphosphor, but we have removed support for python)
should have been removed, so drop the support for the old interface here.

Partially resolves openbmc/openbmc#3584

In addition, when I commited this change, ci reported code format error:

@libmapper/mapper.h
-int mapper_wait_async(sd_bus*, sd_event*, char* [], void (*)(int, void*), void*,
+int mapper_wait_async(sd_bus*, sd_event*, char*[], void (*)(int, void*), void*,

Fixed that.

Signed-off-by: John Wang <wangzqbj@inspur.com>
Change-Id: I0c2d0458a3f55f4671b91f6492e7218ecc3df4aa
diff --git a/src/processing.hpp b/src/processing.hpp
index 53669a5..75a4350 100644
--- a/src/processing.hpp
+++ b/src/processing.hpp
@@ -11,38 +11,12 @@
 /** @brief Define white list and black list data structure */
 using WhiteBlackList = boost::container::flat_set<std::string>;
 
-/** @brief The old associations definitions interface */
-constexpr const char* orgOpenBMCAssocDefsInterface = "org.openbmc.Associations";
-/** @brief The new associations definitions interface */
+/** @brief The associations definitions interface */
 constexpr const char* assocDefsInterface =
     "xyz.openbmc_project.Association.Definitions";
 
-/** @brief Says if the interface is the association definition interface.
- * Supports either the new or old interface.
- *
- * @param[in] iface - the interface to check
- * @return bool - if the interface is one of the association definition
- *                ones.
- */
-inline bool isAssocDefIface(std::string_view iface)
-{
-    return (iface == assocDefsInterface) ||
-           (iface == orgOpenBMCAssocDefsInterface);
-}
-
-/** @brief Returns the property name used by the defs iface.
- *
- * The old interface broke convention and used a lower case property
- * name.  This was resolved with the new interface.
- *
- * @param[in] iface - the interface to check
- * @return std::string - the property name
- */
-inline std::string getAssocDefPropName(std::string_view iface)
-{
-    assert(isAssocDefIface(iface));
-    return (iface == assocDefsInterface) ? "Associations" : "associations";
-}
+/** @brief The associations definitions property name */
+constexpr const char* assocDefsProperty = "Associations";
 
 /** @brief InterfacesAdded represents the dbus data from the signal
  *