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: If9a7314dade153dd7dbd149a76352aca8257839d
diff --git a/functions.hpp b/functions.hpp
index 0cd788e..2fa25c0 100644
--- a/functions.hpp
+++ b/functions.hpp
@@ -12,6 +12,7 @@
 {
 class bus;
 } // namespace bus
+using bus_t = bus::bus;
 } // namespace sdbusplus
 
 namespace sdeventplus
@@ -43,10 +44,10 @@
         std::map<std::string, std::variant<std::vector<std::string>>>>&,
     const MaybeCallCallbackType&);
 std::shared_ptr<void> processHostFirmware(
-    sdbusplus::bus::bus&, std::map<std::string, std::vector<std::string>>,
+    sdbusplus::bus_t&, std::map<std::string, std::vector<std::string>>,
     std::filesystem::path, ErrorCallbackType, sdeventplus::Event&);
 std::vector<std::shared_ptr<void>>
-    updateBiosAttrTable(sdbusplus::bus::bus&,
+    updateBiosAttrTable(sdbusplus::bus_t&,
                         std::map<std::string, std::vector<std::string>>,
                         std::filesystem::path, sdeventplus::Event&);
 } // namespace process_hostfirmware