vpnor: Rename mboxd_pnor_partition_table sources to backend

Change-Id: I6f0fff4ab54e011c1765fc04186e899754787641
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/vpnor/backend.cpp b/vpnor/backend.cpp
index ccda4ec..06aed57 100644
--- a/vpnor/backend.cpp
+++ b/vpnor/backend.cpp
@@ -31,7 +31,7 @@
 #include <stdexcept>
 #include <string>
 
-#include "mboxd_pnor_partition_table.h"
+#include "vpnor/backend.h"
 
 namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
 namespace fs = std::experimental::filesystem;