oemcommands: Always return MB FRU object path for single-host system

For single-host platforms, the debug card always displays the MB FRU
information.

Add a check to distinguish between multi-host and single-host systems,
and always return the MB object path when running on a single-host
platform.

Change-Id: Ia2b41dac01ea53cb5e927186400df94c3130c73d
Signed-off-by: Potin Lai <potin.lai@quantatw.com>
diff --git a/src/oemcommands.cpp b/src/oemcommands.cpp
index f8b1cf4..ba9bbdc 100644
--- a/src/oemcommands.cpp
+++ b/src/oemcommands.cpp
@@ -584,7 +584,7 @@
     if (platform)
         getSelectorPosition(hostPosition);
 
-    if (hostPosition == 0)
+    if (platform == true && hostPosition == 0)
     {
         if (auto path = findFruPathByInterface(
                 dbus, "xyz.openbmc_project.Inventory.Item.Bmc",