sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ibc25db433a6926f7ee43ea83312c3ac14f480c33
diff --git a/extensions/openpower-pels/pel_entry.hpp b/extensions/openpower-pels/pel_entry.hpp
index 4d1bd6c..be8360e 100644
--- a/extensions/openpower-pels/pel_entry.hpp
+++ b/extensions/openpower-pels/pel_entry.hpp
@@ -30,7 +30,7 @@
      * attributes.
      */
 
-    PELEntry(sdbusplus::bus::bus& bus, const std::string& path,
+    PELEntry(sdbusplus::bus_t& bus, const std::string& path,
              const std::map<std::string, PropertiesVariant>& prop, uint32_t id,
              Repository* repo) :
         PELEntryIface(bus, path.c_str(), prop, true),