Patch includes:

1. Support get default value for ref opcode logic.
2. Correct the sample for ref opcode with default value.
3. Refine logic about processing device path info in ref value. 
Signed-off-by: ydong10
Reviewed-by: lgao4

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12774 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/DriverSampleDxe/Vfr.vfr

@@ -645,11 +645,12 @@ formset
       prompt  = STRING_TOKEN(STR_GOTO_DYNAMIC3),
       help    = STRING_TOKEN(STR_GOTO_DYNAMIC3_HELP),
       flags   = INTERACTIVE,
-      key     = 0x1248;
+      key     = 0x1248,
       //
       // Set the defult value, format is QuestionId; FormId; FormsetGuid; Device Path String Token
       //
       default = 0;0;ZERO_GUID;STRING_TOKEN(STR_NULL_STRING),  
+    ;                                                         // goto opcode end flag.
 
     goto 
       prompt  = STRING_TOKEN(STR_GOTO_DYNAMIC4),