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: I86dfa77a53a306b0e868eeb82de30b270704c455
diff --git a/fan_pwm.hpp b/fan_pwm.hpp
index f1dedd6..aa71b9e 100644
--- a/fan_pwm.hpp
+++ b/fan_pwm.hpp
@@ -30,7 +30,7 @@
      */
     FanPwm(std::unique_ptr<hwmonio::HwmonIOInterface> io,
            const std::string& devPath, const std::string& id,
-           sdbusplus::bus::bus& bus, const char* objPath, bool defer,
+           sdbusplus::bus_t& bus, const char* objPath, bool defer,
            uint64_t target) :
         FanPwmObject(bus, objPath,
                      defer ? FanPwmObject::action::emit_no_signals