MdeModulePkg/DebugLibReportStatusCode: Fix hang if format is too long

The previous commit 137ed15511
* MdeModulePkg/DebugLib: Print partial when format string is too long
copies partial format string to DEBUG_INFO buffer but when parsing
the format modifier, the original format string is still used.

The patch fixes this issue.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdeModulePkg/Library/PeiDxeDebugLibReportStatusCode/DebugLib.c

@@ -126,6 +126,11 @@ DebugPrint (
   // Here we will process the variable arguments and pack them in this area.
   //
   VA_START (VaListMarker, Format);
+
+  //
+  // Use the actual format string.
+  //
+  Format = FormatString;
   for (; *Format != '\0'; Format++) {
     //
     // Only format with prefix % is processed.