bmc: move Verification declaration out of single header

Split the interface declaration from the implementation declaration to
make it more obvious what would change to support more implementations.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I6452ad85513dad1431ef946b62936c1cea89c263
diff --git a/main.cpp b/main.cpp
index b4681a6..fc690b8 100644
--- a/main.cpp
+++ b/main.cpp
@@ -25,6 +25,7 @@
 #include "pci_handler.hpp"
 #include "util.hpp"
 #include "verify.hpp"
+#include "verify_systemd.hpp"
 
 #include <cstdint>
 #include <memory>
@@ -100,7 +101,7 @@
 
     auto handler = blobs::FirmwareBlobHandler::CreateFirmwareBlobHandler(
         blobs::supportedFirmware, blobs::supportedTransports,
-        blobs::Verification::CreateDefaultVerification(
+        blobs::SystemdVerification::CreateVerification(
             sdbusplus::bus::new_default(), VERIFY_STATUS_FILENAME,
             VERIFY_DBUS_SERVICE));