clang-tidy: Enable readability-convert-member-functions-to-static

This check finds non-static member functions that can be made
static because the functions don’t use this.
This check also triggers readability-static-accessed-through
-instance check as we are trying to access a static member
function through an instance.

Change-Id: Ia0867db019db8e40e710bdd4025e030061f7a992
Signed-off-by: Pavithra Barithaya <pavithrabarithaya07@gmail.com>
diff --git a/item_updater.cpp b/item_updater.cpp
index 2215b71..641a2a5 100644
--- a/item_updater.cpp
+++ b/item_updater.cpp
@@ -560,7 +560,7 @@
 
 void ItemUpdater::reset()
 {
-    helper.factoryReset();
+    phosphor::software::updater::Helper::factoryReset();
 
     info("BMC factory reset will take effect upon reboot.");
 }