Refactor: move get pmbus access type to utility

The function to get the pmbus access type is common, move it to utility.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I26e7da044c88c1efba141349ee4c18b24cdef81f
diff --git a/power-supply/power_supply.hpp b/power-supply/power_supply.hpp
index e292ca2..550373b 100644
--- a/power-supply/power_supply.hpp
+++ b/power-supply/power_supply.hpp
@@ -265,7 +265,8 @@
     /**
      * @brief The type of the power supply inventory pmbus access.
      */
-    phosphor::pmbus::Type inventoryPMBusAccessType;
+    phosphor::pmbus::Type inventoryPMBusAccessType =
+        phosphor::pmbus::Type::Base;
 
     /**
      * @brief The JSON from the parsed power supply FRU JSON File.