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: I9541d521bf67882215a4a66dce020e38ac2df065
diff --git a/powercap.hpp b/powercap.hpp
index b52ebda..3ef09c9 100644
--- a/powercap.hpp
+++ b/powercap.hpp
@@ -74,7 +74,7 @@
      * @param[in]  msg       - Data associated with pcap change signal
      *
      */
-    void pcapChanged(sdbusplus::message::message& msg);
+    void pcapChanged(sdbusplus::message_t& msg);
 
     /** @brief Get the power cap property
      *