IntelFrameworkModulePkg/FwVolDxe: Ensure FfsFileHeader 8 bytes aligned

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=864
REF: CVE-2018-3630

To follow PI spec, ensure FfsFileHeader 8 bytes aligned.

Current code only handles (FwVolHeader->ExtHeaderOffset != 0) path,
update code to also handle (FwVolHeader->ExtHeaderOffset == 0) path.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>

IntelFrameworkModulePkg/Universal/FirmwareVolume/FwVolDxe/FwVol.c

@@ -4,7 +4,7 @@
   Layers on top of Firmware Block protocol to produce a file abstraction
   of FV based files.
 
-  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions
@@ -510,10 +510,10 @@ FvCheck (
     //
     FwVolExtHeader = (EFI_FIRMWARE_VOLUME_EXT_HEADER *) (UINTN) (FvDevice->CachedFv + FvDevice->FwVolHeader->ExtHeaderOffset);
     Ptr = (UINT8 *) FwVolExtHeader + FwVolExtHeader->ExtHeaderSize;
-    Ptr = (UINT8 *) ALIGN_POINTER (Ptr, 8);
   } else {
     Ptr = (UINT8 *) (UINTN) (FvDevice->CachedFv + FvDevice->FwVolHeader->HeaderLength);
   }
+  Ptr = (UINT8 *) ALIGN_POINTER (Ptr, 8);
   TopFvAddress = (UINT8 *) (UINTN) (FvDevice->CachedFv + FvDevice->FwVolHeader->FvLength);
 
   //