MdeModulePkg: fix issue caused by uninitialized variable

This patch is to fix issue caused by uninitialized local
variable in Pei/Variable.c.

In the fucntion CalculateHobVariableCacheSize(), the local
variable VARIABLE_STORE_INFO StoreInfo is used without
initialization. When the uninitialized variable is passed
to CalculateAuthVarStorageSize() and GetNextVariablePtr(),
the field StoreInfo->FtwLastWriteData might be a uninitialized
non-zero value. Then the code execution will access the
invalid address StoreInfo->FtwLastWriteData->TargetAddress.
This might cause issue.

So in this commit, the local variable VARIABLE_STORE_INFO
StoreInfo is initialized by a ZeroMem() before use.

Signed-off-by: Dun Tan <dun.tan@intel.com>

MdeModulePkg/Universal/Variable/Pei/Variable.c

@@ -1336,6 +1336,7 @@ CalculateHobVariableCacheSize (
   VARIABLE_STORE_HEADER  *VariableStoreHeader;
 
   VariableStoreHeader = NULL;
+  ZeroMem (&StoreInfo, sizeof (VARIABLE_STORE_INFO));
   GetHobVariableStore (&StoreInfo, &VariableStoreHeader);
 
   if (VariableStoreHeader == NULL) {