SecurityPkg/DxeImageVerificationHandler: narrow down PE/COFF hash status

Inside the "for" loop that scans the signatures of the image, we call
HashPeImageByType(), and assign its return value to "Status".

Beyond the immediate retval check, this assignment is useless (never
consumed). That's because a subsequent access to "Status" may only be one
of the following:

- the "Status" assignment when we call HashPeImageByType() in the next
  iteration of the loop,

- the "Status = EFI_ACCESS_DENIED" assignment right after the final
  "IsVerified" check.

To make it clear that the assignment is only useful for the immediate
HashPeImageByType() retval check, introduce a specific helper variable,
called "HashStatus".

This patch is a no-op, functionally.

Cc: Chao Zhang <chao.b.zhang@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2129
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200116190705.18816-5-lersek@redhat.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
[lersek@redhat.com: push with Mike's R-b due to Chinese New Year
 Holiday: <https://edk2.groups.io/g/devel/message/53429>; msgid
 <d3fbb76dabed4e1987c512c328c82810@intel.com>]

SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c

@@ -1581,6 +1581,7 @@ DxeImageVerificationHandler (
   UINT32                               OffSet;
   CHAR16                               *NameStr;
   RETURN_STATUS                        PeCoffStatus;
+  EFI_STATUS                           HashStatus;
 
   SignatureList     = NULL;
   SignatureListSize = 0;
@@ -1802,8 +1803,8 @@ DxeImageVerificationHandler (
       continue;
     }
 
-    Status = HashPeImageByType (AuthData, AuthDataSize);
+    HashStatus = HashPeImageByType (AuthData, AuthDataSize);
-    if (EFI_ERROR (Status)) {
+    if (EFI_ERROR (HashStatus)) {
       continue;
     }