use sdbusplus unpack syntax

Rather than defining a variable and then reading it from a message,
sdbusplus also supports directly unpack-ing from the message.  Use
this syntax instead as it is more efficient and succinct.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I59b1cef85e4e0e5dd14b33a4e1bc15aaef2a8aac
diff --git a/extensions/phal/dump_utils.cpp b/extensions/phal/dump_utils.cpp
index 6d2a666..984e30b 100644
--- a/extensions/phal/dump_utils.cpp
+++ b/extensions/phal/dump_utils.cpp
@@ -136,8 +136,7 @@
         auto response = bus.call(method);
 
         // reply will be type dbus::ObjectPath
-        sdbusplus::message::object_path reply;
-        response.read(reply);
+        auto reply = response.unpack<sdbusplus::message::object_path>();
 
         // monitor dump progress
         monitorDump(reply, dumpParameters.timeout);