Update the return status to comply to PI spec.

According to PI SPEC (Volume3 2.4), GetNextFile() should be return "EFI_NOT_FOUND" instead of "EFI_INVAILD_PARAMETER" when doesn't find the file with related File Type.c

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4159 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c

@@ -148,7 +148,7 @@ Returns:
     //
     // File type needs to be in 0 - 0x0B
     //
-    return EFI_INVALID_PARAMETER;
+    return EFI_NOT_FOUND;
   }
 
   KeyValue = (UINTN *)Key;