BaseTools: Fixed the pcd value override issue.

1. the issue in the overriding value from command line.
2. dec fully value < dec field assign value <
   dsc fully value < dsc field assign value

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/Python/Workspace/DecBuildData.py

@@ -385,6 +385,7 @@ class DecBuildData(PackageBuildClassObject):
                     struct_pcd.TokenSpaceGuidCName, struct_pcd.TokenCName = pcdname.split(".")
                     struct_pcd.PcdDefineLineNo = LineNo
                     struct_pcd.PkgPath = self.MetaFile.File
+                    struct_pcd.SetDecDefaultValue(item.DefaultValue)
                 else:
                     struct_pcd.AddDefaultValue(item.TokenCName, item.DefaultValue,self.MetaFile.File,LineNo)