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: Ief05bd757cffb1453e058a719ee4b060861752e7
diff --git a/phosphor-regulators/test/mock_services.hpp b/phosphor-regulators/test/mock_services.hpp
index 8e3a100..72e981e 100644
--- a/phosphor-regulators/test/mock_services.hpp
+++ b/phosphor-regulators/test/mock_services.hpp
@@ -49,7 +49,7 @@
     virtual ~MockServices() = default;
 
     /** @copydoc Services::getBus() */
-    virtual sdbusplus::bus::bus& getBus() override
+    virtual sdbusplus::bus_t& getBus() override
     {
         return bus;
     }
@@ -150,7 +150,7 @@
     /**
      * D-Bus bus object.
      */
-    sdbusplus::bus::bus bus{sdbusplus::bus::new_default()};
+    sdbusplus::bus_t bus{sdbusplus::bus::new_default()};
 
     /**
      * Mock implementation of the ErrorLogging interface.