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: I96286490697ce5d7fecc1c9c358f5f1d054137ec
diff --git a/mmc/flash.cpp b/mmc/flash.cpp
index e1c5e9c..3bc2ab8 100644
--- a/mmc/flash.cpp
+++ b/mmc/flash.cpp
@@ -23,7 +23,7 @@
     bus.call_noreply(method);
 }
 
-void Activation::onStateChanges(sdbusplus::message::message& msg)
+void Activation::onStateChanges(sdbusplus::message_t& msg)
 {
     uint32_t newStateID{};
     sdbusplus::message::object_path newStateObjPath;