[Offload][Fix] Fix lazy initialization with multiple images

Summary:
There was a bug here where we would initialize the plugin multiple times
when there were multiple images. Fix it by putting the `is_initliaized`
check later.

Author: jhuber6

offload/src/PluginManager.cpp

@@ -155,11 +155,11 @@ void PluginManager::registerLib(__tgt_bin_desc *Desc) {
 
   // Initialize all the plugins that have associated images.
   for (auto &Plugin : Plugins) {
-    if (Plugin->is_initialized())
-      continue;
-
     // Extract the exectuable image and extra information if availible.
     for (int32_t i = 0; i < Desc->NumDeviceImages; ++i) {
+      if (Plugin->is_initialized())
+        continue;
+
       if (!Plugin->is_valid_binary(&Desc->DeviceImages[i],
                                    /*Initialized=*/false))
         continue;