BaseTools/GenFw: Fix parameter format mismatch in scanf functions

According to MSDN https://msdn.microsoft.com/en-us/library/6ttkkkhh.aspx

Format specification '%X' for scanf expects type 'int *', modify the type
of the relating variable to 'int' to keep them matched.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/C/GenFw/GenFw.c

@@ -3158,7 +3158,7 @@ Returns:
 {
   CHAR8  Line[MAX_LINE_LEN];
   CHAR8  *cptr;
-  unsigned ScannedData = 0;
+  int    ScannedData = 0;
 
   Line[MAX_LINE_LEN - 1]  = 0;
   while (1) {