Static layout: support image verification

Add support of image verification for static layout PNOR code update.

Tested: Verify the PNOR code update succeeds with valid-signed PNOR;
        and fails with invalid-signed PNOR or a PNOR tarball without
        signature.

Change-Id: I1aafeb4e8e07eaa16c170f33f4f21940f7c9c146
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/activation.cpp b/activation.cpp
index 2c05ea7..b9cd5ba 100644
--- a/activation.cpp
+++ b/activation.cpp
@@ -176,12 +176,13 @@
 }
 
 #ifdef WANT_SIGNATURE_VERIFY
-bool Activation::validateSignature()
+bool Activation::validateSignature(const std::string& pnorFileName)
 {
     using Signature = openpower::software::image::Signature;
     fs::path imageDir(IMG_DIR);
 
-    Signature signature(imageDir / versionId, PNOR_SIGNED_IMAGE_CONF_PATH);
+    Signature signature(imageDir / versionId, pnorFileName,
+                        PNOR_SIGNED_IMAGE_CONF_PATH);
 
     // Validate the signed image.
     if (signature.verify())